When a search returns the maximum number of candidates you asked for, that's a sign there are more profiles available with those same filters. To bring them in, use the “Add more candidates” button inside the list.

The search re-runs with the criteria you already set, so there's nothing to rewrite: you just say how many more candidates you want.
Duplicates aren't charged
If any of the new candidates was already in the list, no credits are charged for them. That's why the number you ask for and the number that gets added don't always match.