When air passes through a shockwave its velocity decreases but because of compression its temperature increases, the temp increase means that the LSS is now higher, and as the air velocity is down, M of the local flow decreases.

Contrary wise, as applies to your problem, in an expansion wave the air velocity increases but because of the expansion the temperature falls. The fall in temp reduces LSS, and as the air is faster as well, M goes up

These changes occur inside the waves, but remain behind them. Air that has passed through a shockwave has a higher pressure, is going slower and is hotter. After an expansion wave the air is colder and faster and at a lower pressure