Definition: Excessive woofer cone excursion

Could someone describe and/or explain the meaning of "excessive woofer cone excursion"?

The reason I ask this is I am looking to into purchasing a pair of Bryston's 7B-ST amps. These amps are rated at 500 watts a channel. My Paradigm Studio 100's are rated up to 350 watts of input. As I understand it, I could drive my Studio 100's with the Brystons as long as I keep the listening level at a point which does not cause excessive woofer cone excursion. But what exactly is excessive woofer cone excursion?

Thanks,

Dan