I came across this ad looking for fiction and opinion writers as well. It turned me off when I clicked on the link provided for their website and there was nothing there, or it asked me for an authentication code or something. You should respond to their email and ask them your questions about payment and royalties and any other information, such as who owns copyright etc... and then let me know what happened...lol
As you've already submitted something I guess time will tell. At this point October is almost here.