The numbers are gang mold numbers, common on small pieces for which several patterns were "ganged together" on the same match plate for simultaneous pouring. The unique numbers would let quality control know which pattern on the plate was responsible for defective castings should they arise. Apparently a device also used by the counterfeiters. They are also seen on the #0/562 toy skillets, where their odd placement just outside the heat ring on the outer wall of the pan makes the inauthenticity obvious.
Genuine 262/625 pans seem to either have no number or a 1, centered on the handle bottom. The indistinct 1 in the 12 on the fake is likely from the pan the fake was copied from, as gang molds were usually seen limited to four patterns. Most 262/625 fakes have other flaws that make them easily distinguishable from the genuine, The best fake I've seen had a casting quality very close to the originals, but had hanging holes in both handles, something Griswold didn't do.