Current official ASTB-E guidance says candidates may take the test up to three times. The same guidance describes a 30 full-calendar-day wait between the first completed administration and the next retest start, and it makes clear that candidates cannot combine subtests from separate attempts.

That policy changes the way you should prepare. Do not treat the first attempt like a free diagnostic if you can avoid it. Build enough readiness that your first sitting is a serious scoring attempt.