However, not only the distance is important, the kamae also determines whether one is ready to jump forward or not, and whether one can jump far or close.
For example, if one were to strike debana-men, he must not jump too far because it would be slow, and also it is unnecessary since the opponent moves also forward. So, doing a successful debana-men should be aiming at "touching down" quickly with the right foot, in order to be faster than the opponent's men attack.
The separation between the two feet is also crucially important. At to-maai (far distance) and issoku-ittono-maai, the separation must be close to each other. To seme from to-maai, the left foot must draw towards the right foot quickly as the body advances forwards. However, to seme from issoku-ittono-maai ("one-cut-one-step" distance), the left foot should stay put, getting ready to strike at any moment.
It varies with the ability and the height of the person, of course. Generally speaking, when the opponent comes into the "shooting range", the left foot should not move, so that one can strike immediately when there is a chance.