The choice of naming here is somewhat unfortunate, and probably contributes to some confusion.

Level 0-5 is terminology used by SAE to describe the range of fully manual (Level 0) to fully autonomous (Level 5). One would expect that in an article about Autonomous Vehicles, L{0,1,2,3,4,5} would describe the level of autonomy that the vehicle provides, but the article instead uses these to describe arbitrary thresholds of a graph demonstrating the capability of an AI.