Time is Easy- Pressing at 10 seconds in your shop is 10 seconds in my shop. (Except for some variations in air operated presses that may take 1-3 seconds to achieve full pressure)
Temperature gauges on some machines are not accurate and need to be calibrated from a digital pyrometer with a surface probe or paper temperature test strips. ( Infered laser temperature guns do not give an accurate reading on a aluminum platen) Yes, even digital temperature read outs can be wrong and need to be calibrated.
Pressure on a manual machines should be tight and firm to lock down, but your feet should not come off the ground or your back go out.
Pressure on air machines set to 50 PSI should be adequate.
Dollar bill pressure test = Put a dollar bill 1/2 way in between the pad and heat platen and lock the machine down. If you can pull the bill out increase your pressure. Use this test on all 4-corners plus front and center.
Inconsistent pressure can be caused by a worn pad, worn linkage, air leak, bent machine, etc.