Remember, the TPMS sensors are not always actively transmitting to the vehicle to conserve their battery life, so the pressures displayed on the dash may be stale (or even from when you shut the car off after your previous drive) as if the vehicle isn't moving the sensors are in stationary/standby mode. They have internal accelerometers to sense when the vehicle is moving, and when the vehicle isn't moving the TPMS sensors send only infrequent pressure updates to the vehicle to conserve sensor battery life.
If you're concerned one sensor may be off, easiest way to verify the TPMS reading is current is to start and drive the car for at least 30-60 seconds and note the TPMS pressure on the dash right when you stop the car and then immediately check tire pressures with a known good tire gauge.
They'll also go "active" if they detect a 1.2 psi pressure change in 30 seconds, so you could turn the ignition on and manually and slowly air the tire down say 5 psi, then fill it back up, and compare the reading on the dash to your gauge (this is also how you do a TPMS relearn after a tire rotation or new sensor install without an activation tool.)
Remember, the TPMS sensors are more for leak detection and gross out of range tire pressure checks than anything else, so as long as they can reliably track and report a drop in pressure or tell you if your tires are way overinflated or underflated they're doing their job-- it's the old "accuracy vs precision" scenario. Even if the absolute pressure reading is 2psi off compared to a known good gauge, as long as the TPMS sensor can detect a pressure drop beyond a certain threshold over a certain period of time to detect a leak while driving, and show a gross overfilled or underfilled deviation from the recommended filling pressure (usually around +/- 5 psi before it alerts) it's fulfilling its design function for safety and leak detection. They don't need to be accurate to 0.1psi.