I agree with Paul, that's above your graft and could be cut off if you choose. If it were me I think I'd turn that tree into a "triple decker" though...
...When you plant it out face the lower (in-question) branch toward the public eye and it will become a lower level umbrella; your main foliage, which is really looking great, will be the second level, and it looks like you have an upper branch that is rising quite a bit above the middle section of the maple...this can be stem pruned along its length but leave the upper most foliage to become the upper umbrella. I know, I know, I'm weird, eh? :>)_
Shoe (jealous you have such a fine looking tree!)
