Difference between iPack voltmeter and voltage in status display

[Matthew]

While testing a configured iPack I've noticed a significant difference between the voltage measured by the iPack voltmeter card (shows 13.02 V, while sending data, using only internal battery power) and the iPack status which shows 12.7V. In the file sent back at the same time, the header shows iPack voltage of 12.77V. Why does this occur and which voltage should I trust? I have not opened the iPack to measure the battery voltage with a separate voltmeter.

The iPack voltmeter SCM is configured with Scale factor 0.021 and Offset 0.