asterisk users - Feb 2006 - RE: Is my math on traffic/bandwidth correct?

Hi,
 According to what I read, for g.729A 1 line I need 21 kbps.
 Now is it 21 coming in and 21 going out? Or 10.5 coming in 
 and 10.5 going out?
 Assuming that it is 21 coming in my traffic would be 
 21x3600=75600kb = 9450KB /per hour So close to 10M of traffic 
 is coming into my network per hour per 1 g.729 line.
 Is that close or am I completely off ....
 Thanks,
 robert