Hi monbri, welcome to the board!
If you add an expression to your query like:
TrueCount: Count([myField]=True)
(make sure you change the 'total' field from group by to expression.
Depending on how you group this aggregate query, each group will have a new field that counts the total number of 'true's in the specified field. If you need all the 'true's, remove all the fields from your aggregate query so there is nothing to group on but the count of 'true's.
Hope this helps,