Pretty sure your higher bid gets lumped-in w/ a lower bid to help fill the larger quantity ordered in the lower bid when that happens...a package deal so-2-speak...in any case, you come-out a winner. Hows that saying go now !?! 'Don't look a gift-horse in the mouth'.
Happened to me just the other day. Had a bid in a stock at 11.25, ask was 11.26. No fill. The ask moved to 11.29 so I changed to 11.27, and they filled me at 11.25?