Fresh engine's have poor ring seal for one, they take a while to bed in. My 7.4:1 engine was about 8.5 bar. These compression testers are quite primitive, what you are looking for is that all cylinders are equal. The actual reading varies on cranking speed, oil grade, coolant/air temperature etc, which is why they have a green area between about 8-14bar. You can't use them to diagnose pumping efficiency, you need a leak down test for that.