What is credit?
A credit is the platform’s billing unit. Each action carries a flat floor — a planned run, a compile, a replay, a page crawled — and settles at the higher of that floor and the metered model, compute and egress the action really consumed. Reservations are taken before the work starts; work that fails, is cancelled, or parks for a human is charged only for what it actually used.
Why it matters
Higher-of billing is why a cheap action cannot be under-priced into a loss and an expensive one cannot silently overrun a flat rate. It also means the published floor is a floor, not a ceiling — a model-heavy run bills what it used.