One option would be to create a separate measure for purchase variable. Then pass a filter ‘Yes’ in that same measure by referencing your ‘yesno’ dimension. This will get the count of only the ‘Yes’ ones.
It’s works like a having clause for your aggregate measure.
You may then proceed to call the measure which gets the total value in the look, and also call the new measure with Yes condition. Use a table calculation feature to calc the final rate.
Select the dimension which you want the ‘count of ‘ under ‘field of measure’ then pass condition as Yes.
Eg > count of Apples having color = Red.
Here Apple is the ‘Measure’ and Red is ‘Yes’.
Also, instead of Custom filter try the above ‘Filter name’ option from the snap. Call the YesNo dimension here, pass ‘Yes’ under filter value. Mostly it should by default bring YesNo under filter value options to select.
Maybe your total measure field looks like the 1st column. You need to make similar measure for the 2nd column and pass the filter conditions as Yes. Check which dimension was called for the Total count, you will need to call the same one under ‘Field to measure’.
‘Is Converted(Yes/No)’ is not the correct dimension to use as count but only as filter.