When you digg an item in Digg Reader, the story is automatically saved in your “Diggs” folder. We also count and display the total number of diggs for a given story, as a way of indicating its interestingness to the world of Digg users. If you are signed in with your Facebook account, the story will also be automatically posted to your Wall.
Don’t want stories you digg to go to your Facebook Wall? No problem. Just go to Settings, then choose "No" where it says "Share stories I digg to Facebook".