Calculations with virtual table

Hello everyone,

I am working with expenses dataset. This dataset contains 4 columns: the unique id, item id (which can appear multiple times in case few payments have been made for the same item), paid amount (amount paid for unique id on a given date) and payment date.

Last week lbendlin helped me to create virtual tables for total amount calculations
This time, I would like to create a table (or plot) that displays the individual expense, its total amount, and its corresponding percentile. 

I started working on that using below percentile measure (orignally created by OwenAuger  ), but it seems that the total number of expenses in range (which is important in this case) is not calculated properly.

Here's the measure:

Perc_Rank =
var maxdt = max('Calendar'[Date])
var mindt = edate(maxdt,-36)+1
var items = ADDCOLUMNS(VALUES(Expenses[item_id]),"total_amount",CALCULATE(sum(Expenses[paid_amount]),Expenses[payment_date] IN CALENDAR(mindt,maxdt)),"total_items",calculate(DISTINCTCOUNT(Expenses[item_id]),Expenses[payment_date] IN CALENDAR(mindt,maxdt)))
var RankArgument = MAXX(items, [total_amount])
var TotalCount = MAXX(items, [total_items])
var NumberOfLess = FILTER(items, [total_amount] < RankArgument)
var NumberOfGreater = FILTER(items, [total_amount] >= RankArgument)
var RankLower = COUNTROWS(NumberOfLess)
var NumberLower = MAXX(NumberOfLess, MAXX(items, [total_amount]))
var NumberUpper = MAXX(NumberOfGreater, MAXX(items, [total_amount]))
var PercentRankArgumentRank = RankLower + 1
var InterpolationFraction = DIVIDE(RankArgument - NumberLower, NumberUpper - NumberLower)
var RankInterpolated = RankLower + InterpolationFraction * (PercentRankArgumentRank - RankLower)
var PercentRankOutput = DIVIDE(RankInterpolated - 1, TotalCount - 1)
RETURN PercentRankOutput

That's the output table:

And here's the output of my TotalCount variable

I would appreciate any help in this matter.
Many thanks in advance