This WeakAura is supposed to help you keep track of how many (Shadowlands) herbs you have in your inventory, and whether you need to farm more.
This is achieved by setting a farm goal in the custom options, after which the status is shown by the pixel glow around a herbs icon. Green means you have reached your farm goal, while red and blue mean you still need to farm more.
Another feature of this WeakAura is that it records statistics about how many items you get in average from one herb node, which is displayed next to the according herbs icon.