For the safety of the machine, the software will not allow moves beyond the physical limits of the machine. Normally the homing mark is on front left, which limits the usable moves between zero and machine size, and all coordinates will be positive. However, in some cases you might want to have the home position somewhere else. If so, you need to allow movement to negative coordinates. Here, you set the limits.
Please note, that the “Machine Size” is really maximum allowable coordinate. In other words, if your maximum X move range is 570mm but you move the homing mark 100mm to right, the correct settings are Machine Size Max X = 470 and Allow Negative Moves X = 100.
To move the homing mark, you need to increase the amount of travel the machine does after finding the homing switch during the homing cycle. The parameter on TinyG is called zero backoff. To change to 10mm for X axis, send text
$xzb= 10
For Y axis, send $yzb=10.