Build 9925 has been compiled recently, Microsoft usually releases builds that have been tested at least 2 weeks. Most probably they will name a previously compiled build as JTP
Not necessarily two weeks, it all depends on the polish they make at the last minute (eg. icons, texts, etc. which don't impact performance and bug the OS). MS might as well present (without showing the build number) Build 992x (from say one week ago) and release the official JTP to users as Build 992y (compiled yesterday or today) but only if the differences are minor (or a severe last minute bug is discovered). Everything is actually possible. Anyway, who cares the number now as long as it's stable, fast and without UI glitches!! It's still a Beta build after all...