Here's some things you should do anytime a sup is with you, for any stated reason. Always...ALWAYS take your full meal and break times at the suggested times by contract. Never allow the sup to do anything that will increase your SPORH, such as sorting while you deliver, open doors for you, carry any packages, stack the hand truck while you pull packages, etc etc. Visually make notes of anything he does that will pump your numbers.
If the sup demands that he should demonstrate how to do a method, make him show you the same method several times because you don't understand what he/she is trying to teach you. If you suspect your load is intentionally and out of the ordinary loaded better than usual note that and let the sup know that it is so. Of course you should always be using the proper work methods, as trained, as to your best knowledge. There is a chance that you are unconsciously doing some things wrong that you can correct to make your day go better, so do pay attention when they are instructing. However if they seem to be changing the rules, let them know that also. Never accept any comparison of your your performance to that of another, we are all different.
If you have a small digital camera take photos of your daily load for a while, and on the day of the ride just prior to leaving the building.
As far as I know (haven't reread the newest contract) there is no mention of being held accountable for SPORH, over allowed , "best demonstrated" performance, or a specific detail of what a "fair days work" means. There is no mention that the "fair days work" is determined by the company.
The bottom line is that YOU know whether or not you are doing the job to the best of your ability with the tools ( tools here includes decent loads) they provide you. If you are, continue to do so. If not, fix it yourself starting Tuesday morning. Do your job as trained, take your meal and break times as prescribed by contract and if you work over 9.5 three days in a week, file a grievance. The target is already on your back, hold them accountable for their end of the contract as well.
At one point a few years ago, I had a sup ride with me on what he called a space and vis ride, at every stop he stayed in the back of the truck sorting, pulling up sections and determining where to go next. The next AM they had me in the office to rake me over the coals saying I was slacking when the sup was not with me.