I counted for you
CENTER:
16 HSTs per block
9 rows of 7 blocks = 63 blocks in center
63 X 16 = 1008 HSTs in center
BORDERS
4 HSTs per block
bottom and top: 17 blocks X 2 = 34 blocks X 4 = 136 HSTs
each side: 18 blocks X 2 = 36 X 4 = 144 HSTs
Total = 1008 + 136 + 144 + 1288 HSTs!!!!!!!!!!!