PT can only check what Gmail sends back when it requests to see what emails are there. If it's only checking 250 then that's all that Gmail is sending back. I don't know how Gmail works but this has been a constant issue with their POP3 functionality. You can try deleting some emails but Gmail for some reason will still keep sending back these emails, even after they have been deleted.
Are these summaries from PokerStars? If so, I would suggest changing the POP settings to only emails that arrive from now one (see here for directions:
archives/PT2/viewtopic.php?t=23353&highlight=gmail+pop+enable ) and then re-request the summaries from Stars.