probe each main groove, record the shallowest mm. Pattern → Center=over-inflated · Shoulders=under-inflated · One-side=alignment · Cupping=suspension
optional — a photo of the gauge on the tire as evidence
Tread is a long-window check — it moves over weeks of running, so a monthly/PMS reading is right. It gives an independent distance estimate that's cross-checked against the odometer, trips and fuel.