How to cut 10mm?

Perhaps you have LightBurn set for mm/sec rather than mm/min, in which case the laser will be moving 60 times too fast and won’t make much of a mark on anything.

Or it can be set for in/min when you’re thinking mm/min, which will run only 25.4 times too fast.

All those are in Edit → Settings.

With that set properly, the next thing to check is focus, because a defocused beam has very little power.

And then there’s the issue of assist air, without which the beam probably won’t penetrate through the smoke to the bottom of a 10 mm trench.