After 3 circuits: Less than four: Umrah invalidated; continue it, make it up and offer one sheep.
After 4 completed circuits: Umrah not invalidated; no make-up, but one sheep is due.
After 5 completed circuits: The four-circuit threshold has passed; the same rule of no invalidity with one sheep applies.
An ordinary Umrah tawaf has seven circuits; four is the legal threshold for this particular issue.