http://tinyurl.com/75nhxux It did end, or is going to end before that date. "完" stands for "End." Amazon could have possibly made a mistake, but I doubt it, seeing as Amazon most likely receives information of products from their publishers. When the manga is (Ongoing,) that means the series is possibly ongoing in it's serialization, or it's volumes have yet to completely release. Also, for whoever keeps changing the demographic to shounen, Comic Gene is a josei magazine.
Well, that was basically the premise of the magazine. The motto is something like "boy's comics for women." Basically, it's manga that use the style of boy's manga, (shounen manga) but is a magazine for women. (Josei in this case) In reality, it's really just a women's manga magazine that focuses mostly on action manga.