Answer:

Update: It is now possible to count unique distinct values in a Pivot Table. You need Excel 2013 or a later version.

I don´t think it is possible to count unique values in a pivot table unless you add another column to your table or use VBA:  Improve your Excel Pivot Table to count unique values or items

Formula in D3:

Copy cell D3 (Ctrl + c). Paste (Ctrl+ v) on cell range D4:D17.

Setup pivot table

1. Click and drag Array formula to Row Labels
2. Click and drag Count to Values

How the formula in cell D3 works

Step 1 - Construct the COUNTIF function

COUNTIF(range,criteria) counts the number of cells within a range that meet the given condition.

Select cell D3.

Type =COUNTIF(

Select cell range C3:C17

Press F4. You have now created absolute cell references to cell range C3:C17.
=COUNTIF($C$3:$C$17

Now create a relativ cell reference to cell C3.
=COUNTIF($C$3:$C$17, C3)

=COUNTIF($C$3:$C$17, C3)

becomes

=COUNTIF({"AA"; "AA"; "AA"; "BB"; "BB"; "BB"; "BB"; "BB"; "BB"; "BB"; "BB"; "CC"; "CC"; "CC"; "CC"}, "AA")

and returns 3. There are three AA in the array.

Step 2 - Divide 1 with the number of counted values

=1/COUNTIF($C$3:$C$17, C3)

becomes

=1/3

and returns

0.333333333333333 in cell D3.

Count values in a pivot table using an Excel defined table as a data source

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