Countdown timer not showing correct days left

Hi Support,

Today is Dec. 18th
We have problem with the device where the countdown timer is not showing the correct days left.
I have set the countdown timer to show starting from Dec. 11 to Dec. 31 and I get and it shows 5 days countdown.

If I do incognito mode it shows: 16 Days left?
Is my settings wrong? Or what else could be the problem?

Also I would like to know what evergreen means. I have attached a picture of my settings for reference.