Since a 5BW takes 9 quarts, the 3.5 + your 1 means that they only put in 4.5 qts! As long as you had oil pressure and reg oil temps, you probably should be ok. But, crazy to know a 5BW LT4 can run on 1/2 oil charge.
Since I’m not an officially certified GM tech, I use a simple dinosaur method (can you spot it) when I change my oil to remind my old mind how much I have installed,
I also photograph from draining to filling including picture of the drip stick oil line, to reduce chances of warranty denial. 98, best of luck on your outcome