Maybe someone can help me here. The following is from Investopedia explaining a bull call spread...

"A Real World Example of a Bull Call Spread

An options trader buys 1 Citigroup (C) June 21 call at the $50 strike price and pays $2 per contract when Citigroup is trading at $49 per share.

At the same time, the trader sells 1 Citi June 21 call at the $60 strike price and receives $1 per contract. Because the trader paid $2 and received $1, the trader’s net cost to create the spread is $1.00 per contract or $100. ($2 long call premium minus $1 short call profit = $1 multiplied by 100 contract size = $100 net cost plus, your broker's commission fee)

If the stock falls below $50, both options expire worthlessly, and the trader loses the premium paid of $100 or the net cost of $1 per contract.

Should the stock increase to $61, the value of the $50 call would rise to $10, and the value of the $60 call would remain at $1. However, any further gains in the $50 call are forfeited, and the trader’s profit on the two call options would be $9 ($10 gain - $1 net cost). The total profit would be $900 (or $9 x 100 shares).

To put it another way, if the stock fell to $30, the maximum loss would be only $1.00, but if the stock soared to $100, the maximum gain would be $9 for the strategy."

I can't understand why the $50 call is only worth $10. I would have thought it would be worth $11....Anybody?