A single mock exam is a noisy measurement. Question mix, fatigue and luck all move a one-day score by several points.
Readiness blends recent accuracy, coverage across domains, and consistency over time. A candidate scoring 80% on two domains and 55% on four is not ready, even if the average looks acceptable.
Treat 80% sustained over two weeks as your green light to schedule. Below 70%, keep studying — the cost of retesting is far higher than the cost of two more weeks.