This unit will appear the end of your sidebar. As the user scrolls past the end of the sidebar and there’s content to continue reading, it will stick to the top of the screen.
The key to this unit’s performance is short sidebar + long content, so that as the user scrolls down through your content, the unit stays with them for a good long while. This leads to higher viewability, which leads to much higher CPMs.
Since it is lazy loaded, it will not load until a user scrolls near it.
Again, the way to maximize this ad is to have it load soon on the page, and scroll with the user a long time.
That means shorter sidebar + longer content = more money for you. Keep that in mind as you write new posts, and reformat your older, most popular ones.
One caveat: If you are utilizing the Optimize Ads for Desktop Pagespeed feature, you may want to place a sidebar widget (or two short widgets) at the top of the sidebar that will effectively push the first ad "below the fold" and out of the first screenview.
Please remember that if you make changes to your sidebar you will need to reach out to firstname.lastname@example.org to have your ads retargeted.