gos007
Below the documentation's delay list linked by wigog is the following:
Invalid input outside the minimum or maximum length limits of the UI won't trigger an attempt at authentication or key derivation.
I just did a quick test. Repeatedly entered '111' at least 20+ times, it did not trigger any delay whatsoever. Then I tried a 4-digit code, got the 30 second delay after 5 attempts.
So the "minimum length" is 4, as wigog also said, which makes sense as less than that is not secure and would not be recommended.