Short answer
Level-n of the building block view shall be documented in section 5-n of the building block view, where level-0 (zero) is the context view and level-1 your topmost system whitebox.
Longer answer
See the following diagram.
Level-n of the building block view shall be documented in section 5-n of the building block view, where level-0 (zero) is the context view and level-1 your topmost system whitebox.
See the following diagram.