"You shot too carefully".

Hit factor is points divided by time. Shooting all "A"s slowly usually gives a lower hit factor than hitting "As and Bs" much faster.
Time can be less important or MORE important in your standing depending on the stage. Some stages are blazing fast and some are complicated by no-shoots, swingers, drop turners or even loooong distance targets with no-shoots all over the target. Blazing fast may not make up for misses or hitting no-shoots, etc. etc.
"You can't shoot fast enough to make up for all those misses". BUT shooting blazing fast with no penalties and B's, Cs or even some D,s can beat a slow all A score.
Substitute your "POINTS" score and divide by your total time.
Then change your points to a little lower number but also lower your time by .3 or .4 seconds per shot and see the difference.
Hope this makes sense.