Here's a simple answer. If the computer shut off at the MINIMUM number of questions, then you have either spectacularly passed or spectacularly failed. There is no middle ground at the MINIMUM. If the computer goes even ONE question, or more, beyond the minimum, then you were on the bubble between pass and fail and the computer system needed to ask another question to determine if you meet passing standard or not.
You should strive to know the material well enough that the computer should shut off once it has reached the minimum number of questions it must ask.