What do the data of maximum altitude, average altitude, cumulative ascent and descent mean respectively on the Xiaomi Watch S3?

The highest altitude is the maximum value of the altitude value per unit time during the exercise;
The average altitude is the average value obtained by accumulating and dividing the altitude values of each unit time during the movement;
The cumulative rise/fall is the accumulation of the cumulative upward/downward data during the exercise. Take the cumulative rise as an example. For example, when riding, there are 5 uphills on flat ground. After climbing each slope, the altitude will increase by 8 meters. Then The cumulative rise after climbing these 5 slopes is 5x8=40m (the same is true for the cumulative decline, and the cumulative height difference of the slopes is summed).