Why is my adsense earnings different them my youtube earnings?

[David]

I have a youtube channel its very small and I earn very little but it shows that i make even less on adsense then youtube. For example its says i made a life time total of 40$ on youtube and i know you need 100$ to get paid so i didnt go on adsense for a while and i went on today and it said I had a total earnings of 3 dollars in my life time!What do you think is wrong i remember checking 2 months ago on adsense and it said 9$ and that also matched my youtube earnings. But I didnt take any money out because i know you need 100$ to get it.