River 3 Plus energy loss over time

I found this to be pretty interesting - this is a river 3 plus with eb600 with the AC turned off, so just power loss from being online. I don't currently have anything plugged into this unit, so I find it super interesting to look at the decline of battery % over time. And now that I know the battery percentage is estimated - even a bit more interesting to see what the unit is estimating its loss is from 100% to 80ish. I would have thought a smooth line, but it ebbs and flows over the days on how much it estimates it loses.