The height of a jump is a significant value affecting a lot in the sport. The number of fences you have jumped, their height, and the height of the jump itself (as many horses are overachievers and jump way higher than they need to) all affect many things.
Even if you think you are keeping track of the jumps during your session, the reality is sometimes different than you think. How many fences have you jumped? How high has your horse jumped? Your analysis counts these numbers for you.