Behind the two HOTs is the word ONLY. If I can figure out how to add photos, I will post the sticker I place on the front of each and every sub panel I install.
Scott, Send me a Biiiig stack of those in sticker form! I'd love to, for once, go back into a subpanel I installed a year later & not find added circuits with grounds on my neutral bar! I even use the extra long ground bar most've the time so I don't get the "no space left" excuse"! A 225A sub I installed in an office with about 36 circuits & space for 6 more, was ballooned to about 60 circuits with Non-CTL tandems by a maintenance guy!
If you have access to an office supply store, purchase a package of Laser Full Sheet Labels, and print as many as your need. I have that label available in Power Point, or MS Word, or as a standard JPG. Send me an Email requesting it I will try and get back with you.