The minimum distance would be the
shortest range that a punch is effective. That would be 1-inch according to Bruce Lee fans. I've done punches at a "0-inch" range, where my fist is resting on the target and I'm able to execute a punch.
The minimum distance for a kick would be the shortest range that a kick is effective.
The maximum range would be the longest distance that a punch or kick can be done and be effective. Both the maximum and minimum range are defined by a person's skill and ability to do the punch at that range. I can do a zero-inch punch but not everyone can. It doesn't mean I'm more skilled at punching, it just means I'm more skilled at a zero-inch
DK uses his legs when he does his punch. I use waist, shoulder, arm for mine. The components I use are based on my stance. I don't use linear power, I use circular power for my zero inch. But regardless, "Zero inch" is my minimum punching distance.
My maximum punch distance is based on how far I can be away from someone and still punch them. That one is more difficult for me to measure. But if I had to guess it would be the shuffle punch or the step punch using long fist techniques.