About 1% who do so through the hospital procrdures. About a third just stops showing up for followups and hormones. According to the detransitioner, who falls into that category, and has found a small community of similar people, this is what's wrong with the statistic: it's extremely important to not exclude the group that falls of the radar. Since they're not getting hormones anymore, the safest assumption is that they are stopping their transition (because they are) or detransitioning.
A third is a very high amount.
This is the NL btw.