The numbers on the shaft don't tell you anything about spine, at least not directly. All they do is tell you the shaft diameter in 64ths of an inch and tube wall thickness in thousandths of an inch. So, a 2117 is 21/64" in diameter and it's wall thickness is .017".

A larger diameter shaft is generally stiffer than a smaller diameter one. The greater the wall thickness, the heavier the shaft. It gives you an idea of how two different size arrows would compare, but that's all you can tell about spine and weight just going by the size numbers. Still gotta go by the chart to get a good starting point.