Gregg happenings at school

Today I asked one of the secretaries at school to let me know the answer to the question I asked her, so an hour later she sent up a "Secret note" and when I read it I giggled like an idiot. She signed it like this

I couldn't help but notice she wrote d-a-n instead of d-i-a-n (and her n looks more like an m) but that doesn't really matter. I'm sure she just did it to make me smile and that's exactly what it did. :D

Earlier in the day, I went into the teacher that knows Gregg's classroom (Let's just call her Mrs. W) and wrote "Brenna is here" on the white board. I went in a bit later to ask her if she liked my note and she said "I could not decipher it." I said "Seriously? and you know shorthand!?" her reply was "You're really just supposed to be able to read your own shorthand."

Now I'm pretty sure she learned S90 (I think she would've learned it between 78-83 ish) and I'm learning DJS; but are they really that different? I'm confused.