Deutsch and Heltzer indicate (p. 27) that the first word, brk, might be a singular or plural imperative (“Bless … !”). But brk cannot be a plural imperative, which would have been spelled brkw at this time, when final long vowels were indicated in spelling by vowel letters. This was in contrast to the much older system that was in effect, for example, at the time of the inscribed arrowheads discussed above. In that earlier orthography final vowels were not marked, so that there would have been no difference between the spelling of the imperative of brk, “bless,” in the singular (barek, spelled brk) and plural (bareku, also spelled brk).

There are other possible readings of the term brk.
At a BAS summer seminar, BAS member Gerta Cole of Toronto, Canada, suggested to me the interesting possibility of interpreting brk as “Baruch,” the name of the stonecutter.