A question appears on the "featured list" for 7 days from when the bounty is added to the question, regardless of when the bounty is actually awarded.
The bounty can be manually awarded at any time in those 7 days (although you must wait at least 24 hours from when the bounty was added, and the bounty can only be added at least 48 hours after the question was asked.).
It looks like the OP manually awarded the bounty in good time, well before the 7 days were up. (After 7 days, the bounty expires and you only get half, providing you have received 2 upvotes.)
Reference:
https://webmasters.stackexchange.com/help/privileges/set-bounties