This can sometimes happen when you are attempting to find the right size for your wrist. In fact, you may have to go through a couple of returns to get it right. But, if you glance at the size chart (or details about the sizing) and are literally in-between two different sizes, opt for the larger size. The logic here is at least the wristband will don on your wrist. If it is too small or tight, all hope is lost and there is nothing you can do about it.
Then again, this is where the convenience of adjustability comes into play. If this is a consistent issue for you, you may need to narrow your search to adjustable models only. While this does limit your selection, there are still several excellent models out there that utilize an adjustment system.