Sizing can be all over the place, many CX builders believe that your bottom bracket should be higher for better clearance on trails. Independent Fabrication generally have high BBs and thus their seat tubes are quite short so you can still have some standover. My IF cross frame has a 57.5cm top tube and a 54cm seat tube. On the other hand some builders like a tradition road 7cm drop for their BB, thus their seat tubes are generally longer, and their sizing looks much more like a traditional road frame. That said, I assume you are asking about the length of your top tube. Many people run their top tubes a bit shorter so they can be a bit more upright on CX races (or even rides). You may want to consider a TT 1-2 cm shorter (I do, my road frames are 59-60 ideally) but I'd say test ride the frame before you make any decisions.
Hope that helps.
BTW I just joined so I could ask a member a question, but I figured I'd try to be helpful.