now the g729 codec is utilizing 16k for one call if you are using Gatekeeper for CAC but if you want to use locations it is 24k for example if someone ask you to allow only 4 calls g729 using the call manager then the bandwidth will be 96 but if it is for example using gatekeeper it will be 64.
for the CVoice question that you have he gave you 256 divided by 24 it will be 10.666666 so the answer is 10