Point at a crest, hold steady, type the real distance you measured with a tape, then Solve. It back-calculates the true marker size so on-table distances are accurate.
Default 96mm = 6 cells × 16mm (outer black square). Change it here to see distance update live, or Solve to compute it from a measurement.
Crest calibration
Measures the marker pose so ghost scale and placement are accurate. You'll need a tape measure.