You're light on the panel for that usage. If you really want to know more then install a decent battery monitor. This will allow you to measure every DC device power usage for your house batteries. ie A much more accurate energy audit.
AC devices run from a inverter use a lot of DC power. A 800W unit draws 6.7A AC or about 74A DC. If on for only 10 minutes thats 12Ah which may not seem like much. But you have 120Ah to the 50% discharge level. So that one device uses 10% of your Ah. Recommend you keep the inverter turned off and use one of the other non electric options.
Also IF your batteries were 100% on day one it's very likely that they were lower on days 2 and 3. Let's assume 80% so now you have 30% left to the 50% or mark or about 70Ah to the 50% mark.
All of the math aside a decent battery monitor would display the battery charge left (SOC) and you would be well on the road to conserving or upgrading.