Excel Pivot chart with a legend summary table having SUM and COUNT of values

Question

I have a pivot chart display some data I'm interested in. Using a summary table below the chart I can plot the SUM of the values. This works great for me since the data rows contains a 1 if I want to count the value and 0 if not.

Say I have 100 rows from which 20 are marked as 1 and 80 are marked as 0. At this point the pivot chart shows me 20 when I summarize the data using SUM. When I use COUNT it shows me 100.

Is there a possibility to make it show 20/100? To me this is interesting because I plot data over several categories in several years. For one given year and category 20 is scarce, for another it's a huge value.