Ezex
It already shows with knowledge 3 what you are harvesting, for the amount you just have to hover your pointer over the source and its not a difficult task.
At least on Linux, that is bugged. Depending on your zoom level, you have to hover over a completely different part of the window to get the right number. Plus, having to hover over each source to find the highest takes enough time to lose a source you could've digged additionally.