Not the same thing, the number indicates
Lovibond Number, which is how dark the grain is.
15 will be darker than 10, but not enough to really matter.
The "Carastan" part, I don't really know how that designation is different from standard crystal malt. I would assume that it is an imported malt.
Honestly, I think you could brew with it with no real problem in regards to the finished beer.
Gedvondur