I would agree that a 1/4" is a bit large, but only by a hair. Typically it is 3/16" of an inch. If you get water leakage you would use a copolymer strip hard "H" typically as a water deflector. Who measured this? How plumb are the walls?

I have no advice but it seems large to me. I have a frameless shower door and the gaps seem much smaller than the one in your photo. Can it be adjusted?

@milkworkman the walls are surely not plumb it’s an older home. The glass company measured and did the install. And after doing some Research 3/16 is standard and this is 4/16. So not sure if I’m willing to redo at this point. Ugh.

For 1/16" not worth it in my mind and if the walls are out of plumb there is zero chance the installer will redo it. Especially for 1/16" of an inch.