Looking at the MO reputation league I found that it shows up 1767 screens, all screns but the last one show up 9x4=36 users and the last screen shows 27 users. So totally MO has 1766x36+27=63 603 users.
On the other hand, in the profile of the MO leader Hamkins we can find that he is 0,02% overall. But if MO indeed has 63603 users, he should be $\frac1{63 603}\cdot 100\%\approx 0.0017\%$ overall.
The same problem with other users:
for David Speyer is written 0,04% but should be $\frac2{63 603}\cdot 100\%\approx 0,003\%$
for Joseph O'Rourke is written 0,07% but should be 0,005%
for Qiaochu Yuan is written 0,09% but should be 0,006%,
and so on...
What is the reason in such more than 10 times difference?