Welcome to the site pratanakangsadal (that's a long name!),
Also, in case you didn't stumble upon it yet, you can at the top of the forum pages that you are listed as a supporting member (meaning you are recognized as having made a donation) -- so any time you ever lose your license key and need another you can just visit this page and get a new one:
https://www.donation...r.com/Keys/index.phptomos,
we tried an experiment many months ago to give people 100% control of all of their credits and never looked back yet. so the answer is that no credits automatically go to the site, it's up to the donor where to allocate them.
It's a bit nerve wrattling from my perspective, but as a practical matter many people don't do anything with their donation credits and so they will eventually just go to the site by default.