Explanation of the author's (may Allah have mercy on him) statement: "… The Chapter on the Substitute (Badal) …"

The Shaykh :"The Chapter on the Substitute (Badal)", the chapter on the substitute: the substitute is: "the dependent that is intended in itself", a dependent on another that is intended in itself, meaning: the speaker intended the substitute rather than the thing from which it is substituted, but he mentioned the thing from which it is substituted as an introduction and preparation for the substitute, do you understand? And to this Ibn Malik points in his saying: "The dependent intended in the ruling without *** an intermediary is what is called a substitute", so the substitute is a dependent on a principal, and it is the one intended by the ruling, which one is intended, the substitute or the thing from which it is substituted?
The student: The substitute.

The Shaykh : The substitute is the one intended, not the thing from which it is substituted.