Two Different Royalties, Not One
A sync fee and a performance royalty are separate payments, from separate places.
Sync income is negotiated per placement rather than collected by a society: a music supervisor, ad agency or library licenses your composition and your master together for a specific use, and the fee is whatever the deal says. That is the whole payment for most online, app and web placements. But a placement that airs on broadcast TV, cable or in a cinema usually triggers a SECOND, separate royalty: your PRO pays a performance royalty once the broadcast is reported on a cue sheet, exactly the way any other broadcast performance of your composition would. A stock-library sync fee for a YouTube video or an in-app ad almost never has a cue sheet behind it, because there is no broadcast to report. Knowing which kind of placement you have decides whether there is a second payment to chase at all.
One-time sync fee: paid directly, negotiated per placement, no society involved. Broadcast performance royalty: separate, paid by your PRO, and depends on a cue sheet actually being filed — see topic 5.