Counting filtered data (AND filter)

I've created a matrix visual based on this sample data:

PersonID	WeekNr	Service
1			12		A
1			12		B
1			13		A
1			13		B
1			14		A
1			15		A
2			12		A
2			13		B
2			15		A
2			15		B
2			16		A
2			16		B
3			12		B
3			13		B
3			13		A
3			14		B
3			15		A
3			15		B

and the values I present in the matrix is a result of the following measure:

Measure = 
VAR A = 
CALCULATE(
    COUNTROWS(VALUES(Data[Service])),
    ALLSELECTED(Data[Service])
)
RETURN
IF(
    A > 1,
    SUM(Data[Value]),
    BLANK()
)

essentially giving me this:

So what it's doing is ONLY showing results for PersonID and Service, where both services (chosen from a simple slicer) are present during the same week number.

The matrix works great, no problems there at all.

But the client now wants to know, how many distinct PersonID there are in the matrix. I've tried a simple DISTINCTCOUNT(PersonID) but that's of course giving me the total of either value from the slicer. I then tried to use the same logic as in the above measure:

Measure = 
VAR A = 
CALCULATE(
    COUNTROWS(VALUES(Data[Service])),
    ALLSELECTED(Data[Service])
)
RETURN
IF(
    A > 1,
    DISTINCTCOUNT(Data[PersonID])/A,
    BLANK()
)

but this works per line - a total of the results gives me an incorrect total (A manual count for example shows 30, but the result total in the card is 32...).

I hope this is clear enough - basically I need to take the results in the matrix (that works), and make a card displaying the number of PersonID that are displayed in the matrix.