Wokspace buttons function

HI, I have a 3 in 1 printer that I use mostly for laser engraving. Not sure if it is a malfunction with the printer but if I adjust the laser focus and the Z value are showing a different value from 0, as soon as the job starts, the values are changing back to 0. Does this mean that the focus point has changed?
I am wondering if I can find specific details regarding the workspace button’s functions shown below.

. Also how can I maintain the value at which the laser has been focused even when I shut off the printer and turn it back on.