Sam2: Yes, I’m sure that was not the Kesiva that is Assur on Shabbos. The writing is Kesiva, matching up numbers is not.
Interestingly, I remember learning that one can use magnetic letters ON SHABBOS to “write” a message, since there is no actual Ma’ase Kesiva being done. (Of course, this assumes you are not machmir like the YU shitta not to use magnets on shabbos. Even if you are, you can “precut” letters before shabbos and use those.)
I know it sounds strange, and I don’t have the source off the top of my head, but I certainly remember learning it.