Can't find "mail days to sync" option

I just got an iPhone with iOS7 and I synced my two mail accounts from my Mac to it: one is Hotmail (POP) and the other is an IMAP account. My entire inboxes seem to have downloaded to my phone, which is way more than I want or need there. I've read about this "mail days to sync" option but can't find it anywhere in my mail settings. I've poked around forums and it seems to be that this option isn't available for POP accounts (ridiculous) but it seems like it should be there for the IMAP account. Any ideas as to why I'm not seeing it? I really only want the past week's emails on my phone, not everything from the past 2 years. :/

This is all I see under account info for the IMAP account: