This pattern is four beats long, and contains 8 strums. It might look confusing, but just pay attention to the arrows at the bottom of the graphic. An arrow pointing down indicates that you should strum downwards on the guitar. Similarly, an upwards arrow indicates that you should strum upwards. Notice that the pattern starts with a downstroke, and ends with an upstroke. So, if you were to play the pattern twice in a row, your hand wouldn't have to vary from it's continual down-up motion.
Now, try playing the pattern, taking special care to "keeping the rhythm". You should be aiming for trying to keep the time between strums exactly the same. When you get done playing the example once, loop it, without any sort of pause.