Take the advice of an old timer that is now retired after a 45 year city driving career,ending my last few years with UPS Freight.
Do the best you can keep your mouth shut,and follow the company's incentive policy.
"Do what you are told,or get terminated"
UPS uses casuals to see if they are going to be an asset to their program.
In other words they weed out the bad apples,and hire the ones who they think are the best of the best.
UPS's by word is they 'run the tightest ship in shipping'.
Believe me I found that out in short order when they bought out and rebranded Overnite.