Lynn most times these splashes are pourly bonded to the substrate or tub in this case.
I would get a sponge and soak it.
Then prop it up against the spill and leave it there for a good 30-60 minutes. Then try and remove the fill with a scraper. I use an old 2" wall scraper with a super flat edge. You can use a stick. A straight razor. Anything.
The key here is to not scratch the tub with the tool. Often a stick is the safest and with just a little pressure (after the soak) the cement should pop off.
Same principle used here in the last two pictures. A blob of drywall compound I dropped by mistake in picture one on the frameless glass while doing drywall touch ups. I left the rag there for a good two hours and then with no effort wipped the drywall compound off the glass.