Looks like the moment when tableau evaluate the condition you created in the "set 1", it won't consider date filter. so those payers has already been grouped into "In of the set" before the date filter.
in other word, sets filter ran before the date filter.
To fix this we have to let the date filter run before the "set 1".
one way to fix this is to setup the date filter as a context filter by "add to context". it shall be good to go after that.