It's a numeric representation of how much "data" you're sending/receiving (likely bytes, but I can't be sure). Those numbers will vary wildly depending on what you're doing (data sent) and what's going on around you (data received).

If you're in an in-game city, your data received is going to be much larger than if you're in a sparsely populated area. If you're standing still doing nothing, your data sent is going to be zero, or close to it, most of the time.

These numbers cannot be used in any way to determine the quality of your connection, and have nothing to do with your ping and have everything to do with your actions and the actions of those around you. There is no "ideal" for these numbers.