Great question, and while it sounds like this is mostly cleared up, I thought I’d officially summarize how the rain graph is supposed to work:
The blue bar represents the average hourly rate for the time period shown, while the green line represents the daily accumulation (since midnight in the local timezone). The left axis scale applies to both values, but you need to add “per hour” to the rate data. The time period that applies to the blue bar (rate) changes based on zoom level: 1 minute, 5 minute, 30 minute, 3 hour, 1 day. In general the further you zoom in the higher the individual rate values will be, since there is more averaging as you zoom out. Note that when you zoom all the way out, to the 1 day per time step graph, the blue bar (average rate) is not shown.