ActBlue is often set up to track your donations and automatically apply it to other groups, for instance, Biden Victory Fund will send excess to places like the DNC. It's also easy to tell how much one has donated to avoid going over (although they could do better at isolating the primary vs general election portions)

The refund is so people of low income can have more of a voice by contributing to a candidate. When I was low income I filed a PCR.Now I usually don't bother.

Note, it only works for candidates running for state offices or state political parties.

Might as well get my $50 back, then donate it again!