I'm new to archery this year and I have a quick question on arrow shaft "size". To be more precise, how do I interpret the different size designations (i.e. 2117, 2314, 2214, etc...)? All of my archery buddies are being vague on this, whether from lack of knowledge themselves or to keep an "edge" over me, but I have absolutely ZERO clue as to what I'm looking at when I see these numbers. Any help would be greatly appreciated.