Is it correct that this ends the 17th, not the 7th? The description says it runs for 5 days (as usual), which is the 7th, so it feels like a typo.

But don't get me wrong, I appreciate some extra days, since this week is packed to the brim with deadlines, so... don't change it please ;)

Yes it is correct, that's the usual description of the jams, but just below it there's this text:

"This one is a special 15 day long jam to celebrate the 10th jam! THERE WILL BE MORE JAMS IN THE FUTURE!!! (probably at the start of summer)"

Oh wow, I am blind, sorry! I am very glad for this, thank you, it is perfectly timed.
So far, I am really loving this jam btw, I hope you'll continue to keep 'em coming!