Shower Faucet Shutoff Valves

Hey all,
I just replaced the faucet in my tub/shower with a new unit with a single handle. It has 2 screws in the body of the faucet that can be used to shut off the hot and cold water to the center of the unit to replace the spring loaded washers inside the unit. My question is can these be backed out too far? I shut them closed when I installed the unit, and then once installed I started to open them up, I am nerveous about backing them out too far and having a leak or worse. there is a load balancing feature in the faucet that prevents it from getting too hot or too cold, and I think that I have one side closed to much still as the pressure is lower at the faucet than with the old unit.
oh, its a off branded faucet from ACO hardware, "plumbers choice" I think it was called.
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