Charitable contribution limits

Hi,

I am trying to understand why my charitable donations are limited to 50% of AGI and the rest designated for next year's carryover.  

- Cash donations are less than 60% of AGI

- Non-cash (stocks) donations are less than 30% of AGI

- The two combined above are about 58% of AGI.

- TurboTax calculates "Allowed contribution" at 50% of AGI and puts the rest as carryover.

What am I missing here?  Is there an overall limit of 50%?