6x6 inches in photoshop, prints as 6.5x6.5, Why?

I created an advertisement for a newspaper that is 6x6 inches in photoshop (72 pixels per inch).

However, I sent it to the company and the lady told me when she prints, it measures 6.5x6.5.

Why is this? How can I fix this problem? What should I resize it to so that it prints as 6x6 for her?

Thanks!

 

 

 

 

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