The Scale Length of your instrument is the distance from saddle to nut.
The Winding Length of your string is the distance from the ball end to a distance beyond the nut.
The Winding Length of a bass guitar string is typically 2.5 inches longer than the Scale Length of your bass guitar.
Extra Long Scale
Scale Length = 35 inches Winding Length = 37.5 inches
Standard Long Scale
Scale Length = 34 inches Winding Length = 36.5 inches
Scale Length = 32 inches Winding Length = 34.5 inches
Scale Length = 30 inches Winding Length = 32.5 inches
The Total String Length includes the Winding Length plus the Silk/Leader.
Some instruments may require a longer scale string to compensate for the additional distance to a trapeze style tailpiece or a backloaded string through body configuration etc...