Interpreting perfmon

does anyone know what straight vertical lines mean in perfmon? they look like variance lines, but i’m not sure how that makes sense. i would think that variance lines would only apply if there was some kind of averaging going on. does perfmon actually poll constantly and then actually generate some kind of average at the polling interval?

here is an example of what i’m talking about:

http://bobb-bittner.name/perfmon.gif