Nemonater, your comment makes me imagine that you think spongebob is doing something like summoning up dread elder gods

! Or something like that. I can see it right now, spongebob squarepants, the character, summoning up Cthulu! Of course, madness is a
hazard when dealing with the dread elder gods (of Lovecraft).
Maybe your tablet is a precursor of the Necronomicon, telling of the seven gates. Or, of course, it could just be a sales receipt.
On a more serious point, I think you have a neat little
cuneiform text, if you do figure out what and when it is, let us know, unless of course it summons the dread elder gods.
John