Is there any chance you can make it work with including the number of months in all 4 cases? Maybe rewrite it a little bit to make it look less weird? Is this the only translation where it doesn’t make sense to include the %{count} in all 4 texts?
I’m reluctant to change that translation check from “error” to “warning” since it helps a lot with translation quality. I could temporarily disable the check, set the translations and re-enable it again if you tell me the 4 translations.