mk4 sample size 24 or 16 bit?

new to all this and while i was exploring the hercules control panel under the asio tab.
what should the settings be.

sample rate:
sample size:
asio buffer size:

i have been using the mk4 now for around 8 months and it is been rock solid but i just want to better my knowledge

thanks
coley 

You'll find all the needed information in the following document:

http://ts.hercules.com/faqs/eng/her_eng_00445.pdf