Imported photos less than iPhone settings or iTunes storage reports

I'm attempting to transfer photos to the computer to clear off space on the phone.

iPhone Settings -> General -> About reports 2,171 photos iTunes -> iPhone -> hover over Photos part of bar -> reports 2,217 photos

When attempting to transfer either Windows or Mac (Image Capture) -> reports 1,269 photos

Where are the other 800-900 photos? How do I insure that when I transfer and delete from iPhone for space, it'll only delete the ones that synced?