Default Minix neo x7

Just got my x7 today its really good however it stated on the sellers ebay add that its 16gb nand flash storage built in which is the storage side of it i think? but im only showing in settings/storage/total space - 3.94GB, available - 3.35gb, apps - 285mb, cached data - 95.87mb.
am i reading somthing wrong or have i been sold the 4gb model if there is one? If someone could help explain plz i would appreciate it.