1. I think yall are using the wrong base to compare from... thus the results are higher than they really should be...even though small anyway...
It should be a comparison between the cylinder volume with the piston at bottom compared to the two situations with the tester in place compared to the original equipment...

EXCEPT that...

2. The figures which are given for making decisions concerning the health of your engines are derived from tests made by Mercedes Engineers using compression testers themselves... and probably exactly like the ones you are using... thus negating the difference completely.... sending this ' problem' to the theoretical file... instead of being something to worry about...