What do the 2 lines mean?

edbird

There are 2 graphs shown at once, they appear to follow each other, what do the 2 lines mean? Not really an issue but an explanation should be added to the readme.

mgedmin

One line tracks virtual memory usage (VIRT column in `top`), the other tracks resident memory usage (RSS column in `top`). This should absolutely be indicated somehow in the user interface somehow.