For the sake of doing quick and dirty math (yes, I know the numbers will be off), I pulled the VGChartz numbers for Skylanders: Spyro's Adventure on Wii: 1.04 million units.
1,040,000 divided by 55,571 (the number the game has from Nintendo Channel) equals approximately 18.71.
18.71 multiplied by 2,828 (The Last Story's Nintendo Channel numbers) equals approximately 52,912 Last Story copies sold.
Sadly, that sounds just about right for a niche Wii game released at the end of the Wii's life cycle with no real marketing push.