You can try each eyepiece to find which one is closest to focus. When you have found the one that is closest to the CCD cameras focus you are ready to adjust it. If the focusing gets worse, then this eyepiece will obviously not work because you cannot seat it deeper in the holder than it was designed for. If this is the case, start over with another eyepiece or you can alternatively purchase an eyepiece extension tube. There is nothing right or wrong about how you choose to mark them.
Some people even use permanent markers.
The idea is to get a relative focus since fine focusing will be achieved using the CCD software. Focusing a CCD Camera Principles 1. Star images are used to focus. Focusing should be done in its early stages at any convenient resolution. Focusing should be done in its final stages at full resolution using a subframe of the chip.