Yes, that's just the standard nomenclature..."M10" = 10mm. With bolts & studs it'd be "M10 x whatever the overall length is", in mm.
Heads-up, most compression testers tend to read lower than actual combustion chamber PSI on small (72cc & lower) displacement engines, due to hose volume. A good way to adapt is starting with a fresh top end that has full compression; whatever reading the gauge gives you should be reasonably (i.e. usable for practical purposes) reliable as a "full compression" reading that can be used to track any compression loss over the years/miles. With 12" flex hose, my Craftsman compression gauge typically shows around 125psi on a freshly build 49cc motor, 145-ish on a CT70. Your results may vary, depending upon hose and internal gauge volume.
