Who knows. They come from different sources. Without a cultivar, there's a wide range of possibilities, none of which anyone can say with any certainty.

Thanks for responding so quickly! I'll plop it in and see how it does. Not too concerned about it, just thought it would be nice to know.

Also, how fast do jap maples grow? They have some red ones at home depot but they say 20' eventually. Don't they grow very slowly? My Mom has one that has taken forever to get 11 feet.

Your maple might turn out to be red in the spring and/or fall, green in summer, you will have to wait till till next year to know for sure what to expect.

As for growth rate, it depends on genetics (as well as growing conditions, climate etc). Some might reach 20' in less than 10 years, others may take 20 or 30 or more years, but most will pass this mark eventually. Given they can live in excess of 500 years, it is rather difficult to predict the "eventual" height.

Note also that "Jap" is considered a pejorative.