If something is going to occur "within 10 minutes" then it can occur sooner than 10 minutes, or it can take up to 10 minutes. If something is happening "in 10 minutes" then it should happen at the tenth minute mark and no sooner.

Thanks :)

"I will arrive in 10 minutes" means that you will arrive at exactly (or close to) 10 minutes. "I will arrive within 10 minutes" means that you will arrive at any time leading up to 10 minutes, but not past 10 minutes. I hope this helped!