In case anyone was wondering about L2 and the MM's the info below may help you have a greater understanding.
Thank you for your message regarding how the system works.
When looking at L2, you're possibly looking at both the retail transactions and/or trades for the market maker from his or her book. Market makers will reflect customer orders and they're also required to make a market in the stocks. I've included a link about level 2 that might be interesting to you:
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