After the first dove returned, Noah waited seven days before sending it again.
Genesis 8:10 says Noah waited another seven days and then sent the dove out from the Ark. The first release produced no landing place, so the dove returned to him. On the next release, it came back with a freshly plucked olive leaf, showing that vegetation had begun to reappear above the waters.
Noah waited another seven days before sending the dove a third time. On that final release, the dove did not return. The repeated seven-day intervals form a small but precise part of the Flood chronology. They should not be confused with the 40 days of rain or the 150 days during which the waters prevailed.