I found this link that says that dosage of the 10% tablets is 10 mg per kilogram (each 2.2 pounds of weight) twice a day for 5 or more days. Do not put it in the water though, since they usually will not drink it. Give it orally into the beak.
https://poultrydvm.com/drugs/enrofloxacin
https://poultrydvm.com/drugs/enrofloxacin