[Asterisk-Users] Bandwidth, again, can someone check my math?

[Jay Milk]

I want to put a single voice-mail box on a remote server, where I have
metered bandwidth.  Before I do this, I want to make sure it's feasible.
Could someone confirm the following math for me?

G.711, at 64kpbs has a rated network load of 88kbps.  
So for each second of conversation, about 11KB are crossing the wires in
each direction.  
That means for a minute of two-way conversation, 1.3MB of data are
transferred?
That means for each GB of bandwith, callers can leave almost 800 minutes
worth of voice-messages?

Of course, this gets much better if we can get incoming calls on GSM,
arriving at something like 2,500 minutes/GB.

Is that correct, or did I mess up a decimal point somewhere?