How to use it
Tap a number whenever you notice your state change, three or four times on a normal day. Do not try to log on a schedule, and do not go back and reconstruct yesterday from memory. A reading taken in the moment is the only kind worth having here.
What the numbers mean
Use the scale loosely: 1 is running on empty, 3 is the ordinary working state you could hold all afternoon, 5 is the state where hard problems feel easy. Consistency with yourself matters more than matching anyone else's definition, so pick a rough anchor on day one and keep using it.
Reading the analysis
The hourly chart only draws hours you have actually logged, and it shows the reading count next to each average so you can see which bars rest on one data point. Treat an hour with two readings as a hint, not a finding. Two weeks of steady logging usually makes the shape obvious.
Then change the schedule
The log is only useful if something moves. Once your best window is clear, put one hard task inside it tomorrow and push a recurring meeting out of it. The crossover card tells you how much of your current focus time already lands in that window.