Giving the purely literal answer which isn't very helpful: They checked the checkbox to make that level not appear on the homecooked levels list. This is usually only used for packs where you only want the first level to be easily playable, but I suppose it could easily be used on other levels as well.

However! All is not lost. Try the article I'm about to link to, as it works perfectly and is a lot faster than the HCL.
http://www.jazz2online.com/articles/view.php?id=137