I've just checked the ATP rulebook and it looks like you're right, though it's a bit ambiguous over whether or not you need to win a match that has already started by the sign-in deadline - you do if it finishes on Friday night after the sign-in deadline, not so sure if it is halted part way through and resumes on the Saturday.
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GB on a shirt, Davis Cup still gleaming, 79 years of hurt, never stopped us dreaming ... 29/11/2015 that dream came true!