Exactly, jam starts your time the time it says on the jam page. Please note though that the themes will be decided roughly an hour before on twitch. So the jam will probably be more or less start a few minutes early for those that want to get going.
As for contacting xidee, I don’t know what/to whom you are referring. But a lot of us participants and hosts hang around on the dungeoncrawlers.org discord server. (invite on the jam page)