If you are using Quick Fix (2oz.), be aware that 2oz. is the exact amount needed by the lab. And the lab is also aware that Quick Fix is 2oz. The collector might be trained to ask for more than the line on the cup. This is a way to catch you. Or they can wait for you to come out, and say "Oh, two ounces exactly?" and dump it and ask for more.
2 oz is enough sample for any U/A. The collector may ask for more, only to discard the excess. Under DHHS regulations, the collector has to accept the sample if 2 oz is all the donor can submit.
DOT tests require only 45 ml of sample. The sample is then split 30/15.