New
#100
The 390 is what downloaded here as the latest Insider. With the lack of any watermarks on the last couple of builds you know it is very close plus now reaching the 9 days left for free upgrade expiration proceeding the RS1 update by only 3 days. That last week or so is to work out any last minute bugs before anything RTM would be out. Someone at MS decided they wanted everything 100% spotless with 10 before seeing it made the finished product this time around.
Regardless of what number it ends up being it will still be the culmulative end results of all the feedback collected as well as wanting most all bugs already worked out. Nothing is ever 100% perfect however and subsequent patches will always be forth coming later.