I would not be surprised if the "transgender community", to the extent it can have a group preference, prefers to remain basically uncounted. They are a miniscule percentage, and "man on the street" estimates of the size of small groups tend to wildly overshoot. This gives them more influence than they would have were their true numbers known.
On the other hand, there is a chance that the estimates may undershoot. Identifying as transgender is difficult for many people because of the stigma involved. There are also costs; costs for HRT and surgery if you go that route,the cost of replacing old clothes with new clothes, the possibility of emotional costs if friends or relatives do not support. Also, there is anxiety, and one might have fears like, "what if I don't pass?" I think a lot of transgender individuals may not come out or delay coming out for these reasons.
Then there is also the challenge of lack of information. I grew up in a Christian, conservative environment. I attended a catholic school where genders were rigidly segregated. So the idea of "biological sex = gender" was ingrained in me. I did not even hear the term "transgender" for the first time until 1.5 years ago.
