Normally, quotes that have the status Accepted can only be converted into orders through the checkout in the same session as when the quote ws accepted. So, when the customer stops the checkout process and wants to resume it later, the accepted quote cannot be ordered.
Changing this setting to Yes changes the value of the accepted state to a proposal state value. Now the customer can checkout with all the quotes that have not resulted in successful orders yet.
This removes the restrictions of the accepted state but keeps everything compatible. Use at your own risk!
Quote Advanced Settings - Checkout quotes with accepted status
