If you press on it you will see it move slightly. As the others have said, the glue holding the screen on has separated. It's unsightly but no real problem.
Can you possibly seal it, then it would not get worse.
I do not know if you can get some sealant there, there must be a tiny hole that lets the water sit there.
The transparent sealers are useless,, if you can see more with the grill removed then it may be possible to rub some black sealant on the bottom edge working it in with your finger and some lighter fuel to thin it, rubbing it in all along the bottom edge, against the glass and the rubber. Any residue can be wiped off with lighter fuel or petrol leaving a clean job.
My windscreen has quite bad delamination, then again, I wouldn't be at all surprised if it gets a nasty crack and has to be replaced by Autoglass at some point in the not too distant future.....