Can you please try the side panel (navigation drawer, swipe in from the left) in the smart folder?
Should be easy to flip through the different time periods to see if it's just "3 days" for you which is wrong and the others are right... Or maybe those are starred messages and you've got "show starred" enabled there?
As for me, I'm unable to reproduce, tried "1 day", "3 days" and a few others...