Add Matrix numbers

I can't tell whether you have a [Service Year] column (which contains 202007, 202008, 202009 etc.) or whether you actually have columns in the underlying data called 202007, 202008, 202009 etc.  If the latter, unpivot in Power Query so we're just working with two columns, 'Payment' and 'Service'.  I will further assume that these two columns are in the same table. 

Now create a new calculated column which works out the months difference between payment and service.  This will be something like this:

OffsetMonths = (VALUE(LEFT([Payment],4)) - VALUE(LEFT([Service],4))) * 12 + VALUE(RIGHT([Payment],2)) - VALUE(RIGHT([Service],2))

These are the rows in the result matrix you're looking for.