In the diagram, the Fanno line reaches maximum entropy at H = 0.833 and the flow is choked. According to the Second law of thermodynamics, entropy must always increase for Fanno flow.
The Fanno line in the diagram reaches its highest degree of disorder at H = 0.833, and the flow is at a state of maximum compression. As per the Second law of thermodynamics, disorder inevitably increases during Fanno flow.