If it IS visa stamp, then ..

you are right. You don't need to apply for another visa to get back. However---just make sure-- if you just have H4 status but not a visa stamp on your passport, you Do need to re-apply for visa before you come back. It is hard to believe that you get a H4 VISA STAMP valid through nex May, usually they only give Chinese H visa stamps valid for 3 months. Understand the difference between H4 status and the real H4 visa stamp on your passport.