Baytril really should only be prescribed by a vet. Or are you unsure about how rabbit-savvy your vet is? I've checked up on them before just to make sure.
It will be listed under the name Enroflaxacin, and if you enter your rabbit's weight it will give you the appropriate dosage range and any hints or warnings for use in rabbits. The percentage is not important, it's the total grams delivered. Knowing the percentage will help you calculate that.