Hello from another softshell turtle lover! I LOVE THESE GUYS!!!
Yes, yours is an Asian, and they get B I G. You've seen pictures of 2 guys holding up a giant turtle? Well... that's you in about 30 years.
People SAY they grow fast, but I personally have never seen ANY softshell grow quickly. There are about 4 or 5 American species, and a few Asian/African species. The Chinese (yours) and the Florida, and the "rough" softshell are the more common ones.
I have a smooth softshell currently and they are one of the best turtles.
They occassionally do bask (But if they do, it often means the water quality, or temperature are not to their liking) and I would lower the water level in your tank.
Enjoy!