The China specific tariffs (on $50 billion worth of imports) have only been announced. The product list is not even released yet and they indicated it will be at least 60 days before the tariffs are actually imposed. So it would be premature for China to be imposing actual tariffs in response to that now. What China is doing is the so-called "offset" against the metal tariffs, which went into effect against China about 10 days ago. WTO rules allow offsets though technically people should wait for a WTO ruling first, which nobody seems to bother doing these days.