We find climbs automatically from your elevation and speed data — you don't mark them. A stretch counts only when the gradient is sustained, so short rollers and false flats are left out. The altimeter on a watch is noisy, so grade is measured over about 50 m of travel, not between neighbouring GPS points.
Climbing time is the share of your moving time spent on the detected climbs. Compare it with your last rides on the same route: a higher share on a similar route means you spent more of the day working against gravity, so plan the next day's effort accordingly.
VAM is the vertical metres you gain per hour. Your sustainable rate is the best you could hold for 30 minutes, 1 hour or longer — not your fastest short burst. Use it to pace a long climb or a hike: start at or just under the number for the duration you expect.
Power on grades is the median power you produced on climbs of each gradient band, from recent rides. It is a record of what you've done on that kind of grade, not a target. A band appears only after enough climbs, so a missing band means we don't have enough data yet.
Climbing economy tracks whether you produce more or less power for the same heart rate on climbs, over recent weeks against a longer baseline:
A declining trend alongside heavy training is a reason to ease off. It is an estimate from wearable data, so read it over weeks, not from a single ride.