This exercise is from the Core Skills section on Strumming.

By now you should be familiar with the E major chord. Here we will strum it using only downstrokes. Holding just one chord with your fretboard hand should enable you to concentrate more on just your strumming hand. We'll get your fretboard hand working harder soon enough, but first let's get that strumming action sorted!

All 6 strings are strummed - the important thing is to loop the ActionTab and be able to strum along with it in time. Strumming is all about rhythm. Notice that the strumming dots appear beside each string with a downwards arrow in them. Strumming Dots appear simultaneously - because your movement should be fast - brushing your pick or finger down across all 6 strings briskly.

Also notice how a strum sounds, in ActionTabs the real guitar audio allows you to better identify what is being played, when, and how exactly. Use these exercises to train your ear to identify what the guitar is doing.

Once you can play along with the looped ActionTab and strum in time with it (and see if you can play like the normal speed audio), move along to the next exercise...

Important -

Remember the importance of finger poise and thumb positioning to make sure you are getting each string to sound out clearly. Make sure nothing is brushing against the strings and that your fingers aren't accidentally muting any adjacent strings. Also that you use your thumb in the middle of the back of the fretboard for added finger strength and a more acute angle on the strings. It is important to hold a note down hard with your fingers to make it sound properly - the string must be squeezed behind the fretwire.