Wifi sync causes photos to take more space

I've noticed that in iTunes 10.5.3 if I check the box to allow Wifi Sync my photos go from taking 2.1GB to 2.9GB. I can't imagine why this would be, and I have not activated this option to confirm this would be the case (I cannot spare the extra 800MB right now).

Has anyone else seen this? Can someone check/uncheck the box without applying and confirm for me this is not an isolated issue?

Thanks in advance.