question

Maybe, but when the battery is idle, meaning after a couple of hours in an open circuit state...

You have a consumption and during consumption, the voltage is lower.

The battery monitor does not work off voltage, it counts current in and out and relies on being wired up correctly and with the right settings. There are 3 possible reasons for a mismatch, one is in Alex's post above, the voltage charts are resting voltage.

The second is because you have the negative of a user wired to the battery rather than the shunt. The only thing connected to the battery must be the shunt (battery terminal) and the only thing connected to the battery terminal on the shunt must be the battery negative. Absolutely every other negative connection goes to the load/ system side of the shunt.

The third often on boats and RVs with small solar systems is the shunt gets confused between fully charged and low levels of solar if not set up correctly. Either give us a screenshot of your battery monitor settings off Victron Connect or let us know the charged voltage, tail current and charged detection time and also what absorption voltage your chargers are set to so we can confirm.