Overwatch – Number That Appears During Doomfist’s Seismic Slam

The number signifies the amount of "Achievement Points" the achievement is worth. The amount of points directly corresponds with the Achievement's difficulty.

As of right now I cannot find a way to see all achievement points accrued. I don't like the current achievement menu; it shows you your 6 most recently earned achievements but you have no way of reading a description for them unless you find them on the drop down list. I would say achievement points are mainly for personal satisfaction; think of them as a reward for doing certain things. Some people may not feel like they have 'completed' a game until all achievements are unlocked. They give players something to use as a goal.

The number lets you know how many of your teammates (other than yourself) are under the effect of your AoE heal/movement buff. For example, if the number is '5', the whole team is receiving your heals/boosts. If nobody (other than you) is receiving any buffs, the number disappears.

To answer your other two questions:

• Yes, you can influence the number by remaining in range and in line-of-sight of your teammates.
• Yes, a higher number is better. :)