440 what am I missing here?

OK here we go the pistons are speedpro. L-2266F30 forged flat 4.350
Summit number SLP-L2266F30
Compression I tested on #1 got just over 150
#2 got around 157
#8 got just under 160
All were done on a us general tester so thats as precise as I can get
Thanks guys