If Gen Con is the 17th to the 20th... that is 17 days from today (July 31). It is 16 days from Trade Day (Aug 16th). Why are you doing this to me, Gen Con???
I think it's one of those timers that keeps track of everything down to the second (it used to be that in previous years), but they truncate it to the day now. So 16 days 23 hours 57 minute looks like 16 days.
This gave me fits as well.
The timer is correct if you read it as HOW MANY FULL DAYS TO GO (NOT COUNTING TODAY) and if you realize that there are Wednesday events for Gen Con. Counting that way, you end up with a Count of "1 Day To Go" on Tuesday, August 15th.
It's counting down to the day I arrive so I don't mind at all!