Are 0 price rungs allowed? I saw an answer which suggested they are accumulation of all orders outside the llowed L2 market depth, per exchange? for example is this correct?
For example for depth=2
ASK 0.0 5000
ASK 22.1 1000
ASK 22.05 740
BID 22.0 1100
BID 21.90 2902
BID 0.0 4023
so the two rungs with 0 price represent the total price outside the 4 prices closest to the market?