There's no single 'correct' number because it depends on the individual's height and hip flexibility, which is exactly why a test sit matters more than a spec sheet. What to check in person: does a foot land flat on the ground while seated, and can you turn and swing both legs out without ducking or hoisting?
Also look at how wide the door opens and whether the frame is angled in a way that blocks a clean path in. A door that opens close to 90 degrees with a low, flat sill is easier to use than one with a narrow gap or a high lip to step over.
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