As discussed, the impedance track gauge uses the “OCV” data when the cell is at rest. The design must allow some settling time after the load current is turned off to get a good OCV reading. Think of pouring water into a glass.  To get an accurate reading of the water level, one will need to wait until after they have stopped pouring the water in, and the water has settled. Similarly, when the load on a battery is shut off, the voltage recovery will be somewhat gradual. If the OCV measurement is taken too soon, the voltage will continue to change slightly and the reading will be inaccurate. So, the cell must be allowed to relax for some amount of time first.