Happy Bread in Pompeii Day, to those who celebrate.
(I have not checked CIL to confirm the citation / the original Latin. But at least this meme includes a source, which is promising.)
I can't access the physical volume, but sadly the major databases (AGP, EDR, EDBCS) don't seem to have this precisely.
4.8792 seems to document one grouping of the many graffiti from the "campus ad amphitheatrum" (Grande Palestra = II.7.1), which is often confused with the so-called "Gladiators' Barracks" (Quadriportico del Teatro = VIII.7.16), but no bread: http://ancientgraffiti.org/Graffiti/results?global=8792&sort_by=relevance
Here's everything the AGP has from Pompeii and Herculaneum on bread: http://ancientgraffiti.org/Graffiti/results?global=bread&sort_by=relevance
but I should caveat all the above that AGP is not yet comprehensive for Pompeii, and as EDR relies on AGP for graffiti, EDR probably isn't either. I'm not clear on how comprehensive for the graffiti EDBCS is, but it wouldn't surprise me if it lags in this area as well.
That the meme cites an inscription number from the big palaestra near the *amphitheater* (an area that AGP has surveyed) but attributes it to the "Gladiators' Barracks" near the *theater* does raise some concern.
Although, as common as that mistake seems to be (naturally enough), it doesn't disqualify it.
If the bread inscription has disappeared (as many have) since it was collected for CIL, AGP will not have found it during their survey.
For anyone who stumbles across this thread and is not familiar with the acronyms for the databases I used above:
AGP = Ancient Graffiti Project: http://ancientgraffiti.org
EDR = Epigraphic Database Roma: http://www.edr-edr.it
EDBCS = Epigraphik Datenbank Clauss-Slaby: http://www.manfredclauss.de/
FWIW 8792 is in one of the fascicules of CIL IV that is still in copyright and therefore is not available yet online, so someone will need to consult a physical volume to be sure about all this.
viz: https://cil.bbaw.de/en/homenavigation/the-cil/volumes#c128