How to read marginalia on f28v?

[ololololo]

As for that writing on f68r2, I read it as -sy. Which seems to be a rare ending too.

I think the same way, but the glyph itself looks like it was written in one "go" (i.e., as if it should be written that way). 
The inscriptions on the f68r2 (including the one I wrote about earlier) are more interesting by the fact that they can become an indirect confirmation that a scribe who did not understand what was written was really working on the book. The carelessness of these inscriptions may be due to the fact that the main thing for the scribe was to write an incomprehensible text and go do his things.