You might try holding a steam iron over it and giving it a burst of steam the whole length. Sometimes the fabric stretches a bit with a lot of handling. After you have steamed it, let it totally dry and measure again.

So glad this worked for you. I have to remember this for the future.

Personally, I would not try to ease in something that was an inch off. Just seems like too much. Could you add an inner border to make things match up? That would be my choice.