Wing Tsun's "Formula chart" is probably developed alongside with the Muk Yan Chong Form, to illustrate the anatomic correct positions to be structure tested at the Wooden Dummy.
Siu Nim Tau contains eight sections describing the 7 joint structure, Inside-/outside-/Diagonal- positions as Fook/Chaan punches and Jam/Taan/Wu controls,
including the basic structure rules necessary for the execution etc.
To understand the Siu Nim Tau message you must "empty the cup" to get "a little idea" about the simplicity in the human anatomy, rather than the complexity in a traditional fighting system.
Siu Nim Tau trains and tests especially the importance of the elbow joint.