You could use top and left, to position the pop-up, but if there is no container, it will move it based on the entire web page. Sounds like you just want to move it a little further away, so I would add a container around the popup and then set the top and left position in then and make sure you have the pop-up set to absolute. That's a guess, but worth a try.
You could also take a look at the pop-up's positioning and move it as it may already be defined on position within a container already. If it is, that will make it easy, just change the numbers, probably top and left until they are where you want them to be. I am not sure what leader length is, but CSS does have a length property. As long as it is unique ID, you can change it in CSS. So I would go about finding the leader ID and search for the length; it could be set to auto, but you can change it pixels or px in CSS.
If you get stuck, and it's public, you may want to post a link to your site or if it's one page, post to JS Bin - Collaborative JavaScript Debugging