Depth cuts under .1mm

Have a 3018 pro. I am wanting to carve a font on .3mm brass. I am using a 15° v-bit.
I only want to carve to a depth of .05mm. If I set that depth in the setup, the project will not cut
( popup message says “no object to cut”). Seems that anything under .1mm will not be able to carve. I do get around that by setting the Z axis depth to the brass plate. Then when touching the surface with the bit, I jog the Z axis 5 times on the .01mm jog button. When time to carve, the bit will drop down by the smallest setting allowed (.1mm) leaving the actual depth of the cut to be .05 depth I needed. Works great, but why can I not just set this depth in the normal setup method?
Hope this is clear enough. Thank you for any response.