Unexpected behaviour of Calculation item from Tabular Editor

[masplin]

I have a date table and each date is labelled as "Actual" yes or no before or after the last transaction

I ussed tabular editor to create

Current Month = 

SELECTEDMEASURE()

Prev month= 

CALCULATE(SELECTEDMEASURE(), DATEADD('DateTable'[Date],-1,MONTH))

I have a measure

Days in Period = CALCULATE(

                    CALCULATE(COUNTROWS(DateTable),

                        FILTER(DateTable,DateTable[Date]<=[Last Enquiry Date])

                           )

                          )

and

Total Days in Period = CALCULATE(COUNTROWS(DateTable),ALL(DateTable[Actual]))

so days in period/total days in period is 100% for all previous months and X% for the current month. 

In my report i have Actual filtered on "yes" and have selected Jun23

Current month correctly calcuates 30 days in June if you remove the [actual] filter, but May says 22 instaead of 31?  If I remove the report filter for actuals Prem month days in period and total days both say 31. So it seems if i do ALL([Actual] using the report filter it generates right number (31), but not if the ALL is inside the measure?

I assume it is something to do with the DATEADD bit is overriding the ALL, inside the measure, with the 22 days of Jun.

I tried to make a very simple workbook with just these dates, but oddly my Prem Month calcuation item isnt producing any answer. I have no idea why, but the book is here. Test 

Any ideas appreciated

mike