Which specific version of that lens do you have (first-generation, Mark II, or Mark III)? I only looked at the Mark III user manual and there's no mention of macro capability.
I believe what you are referring to is the minimum focusing distance of the lens*.
Note that this distance isn't from the front of the lens to the subject. It's the distance from the sensor itself to your subject. There should be a sensor plane mark (line through a circle) on your camera body.