The German Wikipedia lists the crew for the A7V as 1 officer, 5 ncos and 10 enlisted men. Another 7 to 10 enlisted men in battle configuration (adding messengers, carrier pigeon handler, 2nd rifleman for each MG, etc.).
The article cites a book called "Sturmpanzerwagen A7V : vom Urpanzer zum Leopard 2", which, if you can find a copy, might be able to get you more detailed information on what positions were supposed to be NCOs and which ones enlisted men. Given how haphazard everything was at the front by that time though, what was supposed to be and what was reality might be somewhat different.