That's a good question I don't know the answer to, but I did find this:

http://info.htcomp.net/ragsdale.nsf/aac7d56ca8fd884b852563be00610639/8ac...

To put it simply is this... AMO is found by using a fully set up arrow like you would actually shoot, i.e. it has fletchings and tip and is properly spined. I.B.O. is found using an arrow that is 5 grains per inch, no tip and no fletchings at 30 inch draw and the bow maxed out poundage. In other words if you shot it like that more than a few times you would have a blown up bow. When I bow shop I generally subtract 10 to 15% from advertised bow speed and it will be fairly close to what I set up at. I generally shoot with a 9 grain per inch arrow and 100 grain BH's (for deer) 125 for elk and My draw length is 29.5. Hope this answers your question and good luck.