The belt may "look" new, but there must be settled dust from abrasive friction in the variomatic. It just can't be in perfect new condition after 17500 miles.
What's the width of the belt? It's age (flexibility)?
But in fact, the original Xciting 500 belt lasts quite long. Mine was still savely in it's specified tolerance after 20tkm, but the dealer already told me, it might be out at 25tkm.