That usually means I got zapped while I slept, lol

Imo, the most interesting thing to see in the chart is that you can see when I started to take "zapping to zero" seriously. I now even try to wake up before the rewards come in and zap all my sats away — again. Sometimes, I fail and don't wake up early enough or don't find enough content I want to zap. That's when the lines for stacked and spent aren't fully overlapping.