why does facebook say that x number of people greeted me on my birthday?

[|*awesome*|]

On facebook timeline, i scrolled down and saw that xx people greeted me on facebook. On my emails, it says double of that number on facebook. why is that so? On my first year with facebook, I had only 15 people greet me, but on my emails, it says 40 people greeted me. Does anyone else experience or see this in theirs too?
Sorry, should have cleared that up: the first year of fb, I put it with emails and the 40 people greeted me, but when I go to fb, with the timeline, it says that "15 people said happy birthday to me.

Now with fb for a few years, the number of people who greeted me on fb, is very much smaller than the emails that said happy birthday to me. Why does fb display that when I know that more people have actually greeted me than that?

[Muzzammil]

check both side of your timeline
go on the post stated on your mail