Modification to Time intelligence measure

Hi all,

I'm hoping someone can help with a modification I need to make to some existing time time intelligence measures.

I originally had a large data table (10,000+ rows) of information relating to customer support documents, and how often each document has been used in a support scenario. Rows included the customer name for each document, the RefNum for the support ticket that resulted from each support scenario (RefNum did not contain unique numbers, because a customer support document might have been used in multiple different support scenarios. So each row in the table represented a single support scenario), the Full Name of the support analyst who handled the case, the timestamp 'DateActivityCreated' of when the case was generated, and the title of the support document. Example below:

I wanted to be able to create a summary table, that showed a unique list of the support documents, the customer name for each document, and some measures. Here's an example (the columns in bold are the ones I needed):

And here's how the fields would intended to be calculated:

1) Count Links (Last Month) = count of how many times each support document has been used (based on how many rows it appears in, in the month preceeding whatever month it is currently)
2) Count Links (Last Month -2) = count of how many times each support document has been used (based on how many rows it appears in, in the month BEFORE the month preceeding whatever month it is currently)
3) % Change From (Last Month -2) = This would be calculated as (#3-#2)/#2, except where #2 = 0, in which case the result should be "New"
4) Rank (Last Month) = for the top 20 support documents only, this will show a ranking based on #1
5) Rank (Last Month -2) = for the top 20 support documents only, this will show a ranking based on #1 (in the month BEFORE the month preceeding whatever month it is currently)
6) Rank Change (From Last Month-2 to Last Month) = the difference between #4 and #5

A very kind person put together the below for me, which worked a treat (they used "Date(2020,1,1)" as the current date for testing, which I replaced Now() 😞

Summary = 
SUMMARIZE(
          'Table',
          'Table'[Tenant],
          'Table'[Doc Title],
          "Count Links (Last Month)",
          CALCULATE(
                   COUNTROWS('Table'),
                   FILTER(
                        'Table',
                        AND(
                            'Table'[DateActivityCreated]<=EOMONTH(DATE(2020,2,1),-1),
                            'Table'[DateActivityCreated]>=EOMONTH(DATE(2020,2,1),-2)+1
                        )
                   )
          ),
          "Count Links (Last Month -2)",
          CALCULATE(
                   COUNTROWS('Table'),
                   FILTER(
                        'Table',
                        AND(
                            'Table'[DateActivityCreated]<=EOMONTH(DATE(2020,2,1),-2),
                            'Table'[DateActivityCreated]>=EOMONTH(DATE(2020,2,1),-3)+1
                        )
                   )
          )

)

And here are the measures:

% Change From (Last Month -2) = 
var _lastmonth2 = SUM(Summary[Count Links (Last Month -2)])
var _lastmonth = SUM(Summary[Count Links (Last Month)])
return
IF(
    _lastmonth2 <> 0,
    SUMX(
         Summary,
         (_lastmonth-Summary[Count Links (Last Month -2)])/Summary[Count Links (Last Month -2)]
    ),
    "New"
)

Rank (Last Month) = 
RANKX(
    ALLSELECTED(Summary),
    CALCULATE(SUM(Summary[Count Links (Last Month)])),
    ,
    DESC,
    Dense
)

Rank (Last Month -2) = 
RANKX(
      ALLSELECTED(Summary),
      CALCULATE(SUM(Summary[Count Links (Last Month -2)])),
      ,
      DESC,
      Dense
)

Rank Change (From Last Month-2 to Last Month) = [Rank (Last Month)]-[Rank (Last Month -2)]

The kind person then advised me to go to the table level filter and configure both the values of Rank(Last Month) and Rank(Last Month - 2) with 'is less than or equal to 20':

This all works well, but I'm finding with my live data set that the 'Rank (Last Month)' often returns a duplicate value, because sometimes the 'Count Links (Last Month)' or 'Count Links (Last Month -2)' calculated columns are returning duplicate values in those instances:

What I'd like is to be able to do is have a completely (as much as I can) unique 'Rank (Last Month)' field, by adding the followig logic (in bold):

Rank (Last Month) = for the top 20 support documents only, this will show a ranking based on the following rules:

1) Count of how many times each support document has been used (based on how many rows it appears in, in the month preceeding whatever month it is currently)
2) Then, count of how many times each support document has been used (based on how many rows it appears in, in the month preceeding whatever month it is currently, -2) (i.e. the previous month)
3) Then, '% Change (From Month Prior)
4) Then, base the ranking on which Doc Title appears first in the alphabetised list.

I'd really appreciate any assistance here!