Umm this may have already been answered, but I've found no difinitive guide to say otherwise.

Now, I've been quite busy on Emerald, {because I'm filling up Box... trying to get that Pichu -.-} So, I decided to get a good Jolly Houndoom. I grab my Houndoom from Col-breeding it with Ditto, and yay, getting a ton of SunnyDooms.

But here's the weird thing. I bike from Verdanturf to the beginning of the beach at Route 118-around 260 steps on bike {calculation may be wrong...}

Now. I know Houndoom takes 5120 steps, so that's like 2560 steps with Incubator attached {That's my Slugma}. So..

Why are my eggs hatching after only two trips? A trip equals going from Verdanturf to the beach only. Seriously, I'm up to around 50 Houndooms. In a very short time, like 8 minutes I believe. Why are they hatching so fast? Is there anything that says hatching a Pokemon with the Flash Fire type also accelerates its hatching? Or do I have some sort of cool glitch. Note this only works for Houndours, Eevee is pissing me off because it seems like forever.