grounding wires overkill
Here you have two ground wires: one coming from the cable, and one from the light ballast.

One possible procedure is to twist the two ground wires together, then screw the twisted portion against the fixture.

Alternatively you can screw both wires into the fixture separately, but you will need to find or make a second ground screw.

The fixture should be grounded, so solutions that just connect the two ground wires but do not attach securely to the fixture are not good.