Unless your object is directly under the camera, things can be off by up to 1/4". Best way to avoid misalignment is is to have your octagon and initials in the same file; load it into the GFUI, ignore the initials and cut the octagon shapes out of a piece of cardboard, then take out the cardboard octagons and stick in the ones you actually want the initials on, without moving the piece of cardboard. Then in the GFUI, ignore the octagon cuts and score the initials. At each step, make sure your material height is set correctly, for best alignment.
There’s lots of discussion about alignment on the forums. Here’s a thread to start with that might help: Glowforge Interface - How to Get Perfect Alignment (Yes, perfect!) 🤔
Good luck! 