We're having an issue where our DB keeps running out of capacity. Currently our ExchangeSyncIDMappingBase is reaching 10GB, and I can't figure out a way to reduce it.

I've deleted all the records I can, but it's not reducing the capacity by much. Can anyone tell me why this is so large? Or how I can safety reduce it?
I know this is where the Exchange sync IDs are, but we don't sync that much data (activities, emails, contacts) from Exchange. So why the heck is this so large?