Dear TenGauge
Don't know where did you get the machine, if it is from China, there are three parameters will affect your engraving depth.
Laser Power: Bigger power, engrave deeper
Marking speed: Slower , engrave deeper
Pulse frequency: Lower, engrave deeper
Normally we don't have the measure tools to measure exactly if it is 0.1mm or 0.3mm depth, but you can try with 90% power, 500mm/s speed, 20KHz pulse frequency, and make some adjustment base one the result. If you still can not engrave deep, you can engrave more than 1 time in the same piece.
Hope this will be helpfull.
Warm regards
Eric