Bunny being bitten by a bunny do you mean?
I would imagine it depends on the situation for how long, and also the antibiotic for how long it stays in the system.
Given that Baytril is the least effective antibio, but I have had that for a rabbit wound on another rabbit, we did a 7 day course. Once you start it, you have to finish it, like with people, even if everything looks good.