question

Hi Judith. As you've found already, the BMV is a highly configurable device. Accurate when configured with accurate parameters.

Your "-2W" is likely just a zero-error, and the manual describes how to deal with it: https://www.emarineinc.com/pdf/VictronEnergy/BMV-700%20Manul-English.pdf See section 4.2.09 The BMV712 standby spec is '<1mA', which is tiny, and if your batts are isolated, likely irrelevant.

Unfortunately a lot of consumer batts don't provide much help setting this stuff up. Just guessing now, but your 'Tail' and 'Peukert' might be a little low, and the 'Efficiency' a little high (variable in itself, as it has to account for batt self-discharge too). From memory now, but Victron for agm suggest 1.25 for Peu and 0.95 Eff as suitable kickoff points.

Victron actually has a 'Peukert Calculator', but relies on at least a couple of the batt maker's C/Ah figures. Most start/general purpose batts don't show those, and I can't see them either on a quick look at yours.

Familiarity with the manual and what these things all mean will help. Don't rely on SOC til then, but if you go aboard and your standing agm's are 12.5V or greater, then they're ok.

Fair winds..