It is a manufacturer's mark from the outfit that made the lower. Between that and the checkering on the pistol grip, these don't look like they have any time on them.
Makes sense to me.
At any rate, I don't think the emblem is important. What I think the person who circled in red was trying to point out is that the rifles are not loaded - no magazines.
“UID markings - Unique IDentifcation labels that are mounted to each weapon nowadays.”
See Porkchop’s post #1,539