compression sb 402 stroker magnum

I have a technical question for you guys ....
My engine is a bone stock 2002 mopar magnum crate 360 stroked to 402 cubes.
spec sheet says it is a 9:1 compression engine..
well how can that be if I just did a compression check on it hot and the butterflies open on the carb >>> all cylinders were at 180 #'s cranking pressure . seems ways high i thought .
cam is a hyd roller 288-292 duration ... 501-513 lift . not sure on the lobe sep.
RT cast iron heads 2.02 's