Its more to do with limitations on output space on the "graph module" that outputs the pretty bars Im afraid.
Its already been fairly heavily modded to allow the display of info that it does, and the hover function for the total wasnt something it did by default, but something that had to be played with to get it to do what it did.
When I broke down the totals for the individual ISPs I had a bit more room to play with, but on there I was actually more concerned with splitting it into the relevant sections.
It probably would be possible to do this but would require an amendment that is a lot more complicated to do than it may look since the module does have some limitations:(