Donations to Charity in 2021

I am using Turbotax 2021 Home & Business.

I am Married filing jointly and using Standard deduction.

My donations are above $600, but line 12b is limited to $300.

I thought the limit should be $600, am I missing some other details?

https://www.irs.gov/newsroom/expanded-tax-benefits-help-individuals-and-businesses-give-to-charity-d...

https://www.irs.gov/pub/irs-pdf/i1040gi.pdf