The first set of stats had as a population = respondents to a survey by the HRC under contract to the insurance industry, with a fudge factor. Read people who were members of or supporters of the HRC extrapolated from figures by people like psychologist Peggy Cohen-Kettinis several years ago..
The other, larger numbers came from a different set of stats where estimates were made by using HRC figures and adding a fudge factor (as I said I do not know how they got it, probably a WAG) where they expected that only a fraction of people would or could respond. I erred in my use of the "US poplulation"

. It should have been "all US citizens who had ever had surgery anywhere since 1996 or would have it in the near future" vs. the US population which was less than the 2010 population estimates, which would be a different number and from a much different population. I still do not trust the numbers. I suspect they were a tad high then, though might be nearer now. This was a group again wanting to show the "might" or lack of it of a minority population.
As for the proportion of F2Ms vs. M2Fs, that is actually based on numbers of people applying for and completing surgery, not the number of folks that might be F2M. As I said, surgeons, most recently Dr. Brassard, indicated the proportion was about right in his surgery in Canada, where the surgeries are paid for by the govt. health care program. I had direct contact with Dr. Bowers (Oct. 2007) and Dr. Brassard (Nov. 2010) on the question, and email contact with the office of Dr. Zukowski in Chicago (July 2009).
Also recall the statistics of the first set from the HRC; I said they were "current" as of 2006-2007. There are apparently many cders who are very closeted or may use cding as a prelude to sex or a substitute in real sex with a partner. But they do not find their way onto the web as respondents on a forum, of if they do, are more lurker than participant. They also do not go out. Judging from my later interviews, I think the numbers really haven't changed too much.
Transgenderists (non-ops) living in role are hard to separate from preops who are living in role but can't swing the money for the surgery, so this group I think is actually larger for that reason.
For TS, there are a lot of obstacles to having surgery in the US, ranging from inability to hold jobs during transition and loss of income, to interpersonal relations within families. It does happen, since there are ways so that a few folks can get their surgeries, often at the cost of significant parts of their lives, their livelihood, and their property.
I think if we could sample the population using only transitioning in terms of top surgery and hysterectomy as the criteria for F2Ms, followed by name and birth certificate change, then we would get a more narrow gap in the proportions of F2Ms vs. M2Fs. Most F2Ms do not waste the money for inadequate results from the "pole" construction.
And remember these are statistics. As such they consists of "Lies, damn Lies, and government reports" unless they agree with ones preconceptions.
When I was at Dr. Brassards, he had 12 M2Fs and 2 F2Ms in two weeks. They guys were there for reconstructive surgery, not mastectomy and hysterectomy. Those were prior surgeries. Few he said find the "pole" reconstruction to be useful or adequate. Both these guys were there for reconstruction and had surrendered skin grafts from the arms and legs for the process a week down the road after they had healed some from the initial surgery. One was in his mid 20s, the other in his late 30s, so pretty young, and both had been on T for more than 8 years, 20 years for the elder of the two.
I spoke with one 43 years old F2M friend just yesterday afternoon after we team taught three classes, and he said the expenditure (over $100 grand for inadequate results) was just too much, so he had put that aside because he was a man without it. If he had all the money he needed for the surgery and to take care of the two kids, one grandkid and wife, then he MIGHT consider it. And at 43 and both kids near leaving the nest, he has time. Others at other times have said the same general thing, though their familial circumstances were different. Clitoral release, that gets "erect" to about 4 inches and gives great sensation is enough for most. Others have a "scrotal sac" constructed with labia material and silicone implants to provide a more normal appearance, but the uretha remains in a more female location. That is one improvement they would like to have so they could stand at the urinal instead of using a stall.
Carolynn