I don't know how that particular tester works but too test for the
gasket leak the air must remain constant to allow the air bubbles to
reach the fill tank. About 5 min. per cylinder. Some of the air is going
to leak between the ring gap into the crankcase. Leave the cap off the
fill tank and only apply about 15 lbs. max of air. If you apply more you
stand the chance of blowing the hoses off. With this test you'll see any
leak in the system if it leaks past the gasket.