This is a mistake that has lead many conspiracy theorists to think the autopsy materials are false. They are not. That photo is taken after the scalp and hair has been manipulated to show less damage than was actually there. The cowlick bullet had created a huge flap of loose scalp, with the cratered skull underneath, this is partially apperent in that photo, but the scalp has been stretched out to cover a lot of the actual underlying damage. The cowlick entry caused the large flap on the right hand side, and the eop entry, which was around the area of the hair line where the white object is in that photo, exited the large defect caused by the 313 cowlick bullet due to the fact that Kennedys head was almost horizontal when it struck by the 2nd shot:
At around here
http://zapruder.site90.net/?#f340|lauto|tauto|w830|h820|mt0px|ml0px|v0
Kennedys head is virtually horizontal. The bullet struck the eop and exited out the large visible defect in this frame, probably going on to strike Connaly whose back and left thigh is exposed in the direct line of fire at the exact location he was hit due to him taking an almost feotel position.