10:1 means that for every 10 he loses, he needs to win one in order to breakeven. thus he needs to win one out of every eleven. 1/11 = 0.9, or 9%. consider it like this. we'll do it 11 times and if he wins one out of 10 (which translates to roughly 9% of the 11 times) then he will break even.
the first one we win and profit our $1.40 (the pot)
the next ten we lose $0.14 cents. 10 x $0.14 = $1.40

in reality it is far more complex than this because our calculations dont factor in how much can be bet on the river, and how often we will win or lose when that happens. because of this i'd advise ignoring all of this post and checking out some of the threads in the beginner's digest which will explain these to you far better than i can.