You're not going to have issues in a mile unless you live close to the North Pole. You don't. Where you will be more likely to have issues is if you create an A+ line with a John Deere system and then create and A+ line with a non John Deere system using the same heading and try to have the second system follow the first one exactly. It won't work because they calculate things differently. As was mentioned, even in that situation you might not notice in a small field.