Spotify Windowing is an exclusive release feature that allows you to Get your music on Spotify Premium for two weeks ahead of your official release date. This means that Spotify Premium subscribers will get to listen to the new release two weeks earlier than the free tier.
Spotify Windowing cannot be added to a release after it has been distributed to stores. You need to set up Spotify Windowing during the upload process to take advantage of this feature.
This option can only be applied for releases that have 7+ tracks or that their total track audio length is more than 30 minutes.