You can give a reputation to the same person only if you have repped 5 persons after that. Having said that, you can give a maximum of 10 reputations per day. Rep power is calculated on the basis of how old a member is in this forum. A person may have only 30 posts, but if he is 4 years old in this forum, his rep power may be 40 or 50. BTW, the exact method of calculating rep power nobody knows besides the admin. I think it increases by one per month or 2 months. Also, the method to calculate it keeps changing from time to time.
We've come too far to give up who we are
So lets raise the bar and our cups to the stars
Solange: You like married women... don't you, James?
James Bond: It keeps things simple.