If a user offers to pay $20 for greens and I choose an offer with 1/4 credit, will the user pay $5? Or, is only 1 credit offers accepted?
It depends on the site. Most times, though, you need to get a full credit.
no, because he won't get paid either for the .25 you complete, he needs 1 FULL
What if I complete two 1/2 credits?
Then that will add up to 1, and that's fine.