When you begin to start twisting up one end to start a loop, do you always measure in like 8 inches and start the loop there? I mean do you always start at the same point? The more you move in the shorter the string will be. But after many strings you will get the hang of it:)
You can't really go by the string length #'s marked on the jig, if there are any, because everyone makes a string a little different. If your string is too short, move out another hole or two and try again. I measure from string groove to string groove on the bow and then correlate that measurement to the #'s I have written on my jig.