Error in Charitable contribution deduction for non-itemizing marrieds filing jointly

For 2021, non-itemizing marrieds filing jointly can deduct up to $600 in charitable contributions. Turbotax enters this in its worksheet correctly. However, in the Review section, it removes the $600 and changes it to $300, thereby stating we owe more taxes. I believe this is a software error. I thought turbotax guarantees the highest return (?).