Recurve bow's length is measured by following the profile of the bow's back from one end to the other, not in a straight line between the tips when the bow is strung. Lay a cloth tape along the back of the limbs and across the riser to measure your recurve.

The bow string will always be shorter than the AMO length marked on the bow.

I've included a link to a page with some of the AMO specifications, including Bow Length Standard, but I don't know how helpful it'll be to you because I don't understand it either. I think they were smoking some whacky tobaccy when they came up with the whole bow length standard thing. [8D] There are some other specs on the page that are good for shooters to know though, so it's far from a waste of time to read through it.

Rule of thumb, a bowstring for a recurve will be about 4" shorter than the bow's AMO length (which is what you've got). String length for a longbow will be about 3" shorter than the bow's AMO length.

http://peteward.com/AMOStandards.pdf