First of all it tells the time. ;). It shows the battery drain over time.
Start:= the time you started this clockface. I expect you to know the day.
Used: the “amount” of battery used in % . When you have charged you battery it can add up to over 100 %.
hours:= the total amount of hours the clockface has run.
Check:= the time the clock has last seen a difference in % of battery load.
min/%:= the amount of minutes the clockface took to consume 1% of battery lately.
Hours:= the total of time a *full* battery can persist before you have completely drained it.
The down-going line (the slope) in the middle gives the % of battery for the last 12 hours.
The histogram at the bottom gives the amount of battery drain in time.
Screenshots are real photos, adapted to screen format.
Overnight the screen is off, therefore it takes 154 (!) minutes to take 1% off battery.
I know WiFi drains battery hard, also screen on. GPS and heartbeat not so much.
The peak at 14:30h is a result of charging the battery. This is a normal curve.