Just wondering if this is how you did the compression test:
remove all spark plugs
ground ALL spark plug wires to the block
hold the throttle Wide Open
crank the motor over until the PSI gauge stops rising; repeat for each cylinder.
It's possible to get significantly different compression numbers if the test is not done like this. Probably if all plugs were not out and you were not holding throttle Wide Open the numbers you get would be a little lower than actual.