Leveling
Every monster you can reach at a given level, and what one kill is worth as a share of that level. The gap penalty is applied, so what you see is what the server pays.
This is the ceiling of a map, not a forecast. The height of a bubble is what one kill pays you at this level, the width is how many of that monster stand in the world at once, and the colour is the two multiplied: how much of a level is on the ground there. What it cannot know is how fast you kill, how far apart they are or how hard they hit back, and those decide as much as the number does. Click a bubble for the monster itself.