Three different limits exist, and they protect different things.
Draft rate limit — free users get 20 draft generations per hour, Creator 120, Pro and above unlimited. Final renders are never rate-limited on any plan, because those are paid for in credits and limiting both would charge twice for the same scarcity.
Concurrency cap — how many generations you can have genuinely backlogged at once, from 16 on Free to 192 on Enterprise. A burst you just submitted does not count: a twelve-view model sheet is one action, not queue abuse. Anything stuck for over 30 minutes stops counting automatically.
Daily credit ceiling — a rolling 24-hour blast-radius limit against a runaway loop or a compromised account. Free 600, Creator 3,000, Pro 12,000, Studio 40,000, Enterprise none.
Hitting a compute cap never costs you anything — your balance is untouched, and the message says so.