Pump gas compression

Dynamic is effected by the cams timing when it opens and closes the valve during the pistons travel. The can build more or release more compression driving the PSI in different directions which can be very different that just a dead straight up mathematic number of static ratio.

It is possible to run a 12.5-1 static ratio engine on pump gas if the cam timing allows it. On the flip side, a 9.0-1 can ping to high heaven if the cam is wrong.

A static figure is a starting point to red the possibles.
Dynamic is much better a d is often seen in cylinder see PSI.
Couple it all with the cams known events (timing) a d the gas o game can be figured out.