I counted 143. You have them stacked 12 high, and 11 across, with an extra 11 on the left side.
So, (12x12)-1 = 143, or (12X11) + 11 = 143.
And 143x50 = 7,150 rounds, assuming 50 per box.
EDIT: Just realized they may not be yours. But regardless, my calculations are right unless my eyes are playing tricks on me.
This post was edited on 5/1 at 10:09 pm