Spine is theamount of flex or bendof an arrow shaft under certain conditions. When you shoot the arrow it flexes as it leaves the string. If it flexes the correct amount then you have a correctly spined arrow and it will shoot best. If it doesn't flex enough then it is too stiff, too much flexing and it is too weak and either one too stiff or too weak is not ideal. A hunting arrow is usually set up with a slightly stiffer spine than a target arrow.

Someone can look up your info if you list your bow model and its' current setup and your arrow model with its' length and tip weight along with fletches.