To understand the capabilities of market makers, one should know the limited market depth available to any participant:
1) Data featuring the nearest (best) placed 10 bid and 10 ask limit orders shows the price and number of contracts (Level 2).
2) Data featuring each transaction made shows the price, time, and number of contracts (Time & Sales).
CME Group market makers use the full market depth available to the exchange, namely:
1) Data featuring all existing placed limited orders
2) Data featuring all existing placed stop orders
3) Data featuring all open positions: price, volume, and side of order (buy/sell)