Here you can control access to the download. You may select different user roles. Only the users from selected roles can download the package. Select All Visitors if you want to allow everyone to download the package regardless of their role/privileges. If you want to make a package login protected or members only, select all user roles here except "All Visitors".

Additionally allowed/selected roles from associated categories will be merged with package access. For example "Category A" and "Category B" selected for "Package P" from "Categories" meta box, "Subscribers" has access to "Category A", "Editors" has access to "Category B", "Authors" is selected for "Allow Access" field in "Package P".
Now,

Effective Access to "Package P" = Selected roles in "Allow Access" field + All selected roles for "Category A" +  All selected roles for "Category B" = Subscribers, Authors, Editors