The letter on the info strip at the bottom of the photo indicates what type of event caused the photo to be taken.

M = Motion-triggered

E = Event (a photo taken at a scheduled time or a manual photo)

T = Time-lapse

F = Photo taken after format SD card request

S = Requested photo (available with Real Time ON for 3G Cameras, or the Take Photo Now command for GoLive and GoLive 2)

U = Firmware Update Successful