Using Functions in Record Summary?

Using Functions in Record Summary?

I'm trying to get the record summary of Record Type A ("Players") to e.g. show the sum or count of all entries in a field in a connected Record Type B ("Games"), so that I can show the total wins that player has made, or total games they have played. I can access the field (e.g. ${Record_a_Match_Date_of_Match.They_Won_the_Match}), and it returns a comma-seperated list, but I can seem to perform any functions on it (e.g. sum(${Record_a_Match_Date_of_Match.They_Won_the_Match})). Is this possible?