Hi Dave, yes that second mute is a muted strum of the open strings while you change chords with your fretted hand.

Also note that the first 3 chord changes (E, G, D) all happen right on the beat, while the change to the C chord happens on the and-of-2 - which is known as a "push" or "anticipation."

One strategy is to just try one strum on each chord change, and make sure you are changing on all the correct beats. Then experiment with filling in with the strums in between.

Hope this helps!

Let me know how it goes,

Mike