Charity donation

I made a $600 Cash donation to a charity. 

I entered this in TurboTax; and it shows that $0 is deductible. 

I looked up Charity Donations on the IRS.GOV site, and it says that "up to $300 of cash donations are deductible". 

I checked with a friend of mine also using TurboTax, with a much lower income than mine, and the same thing happened to her. 

Is this a glitch in TurboTax? 

Patrick