Becuase there is no GDP figure in 1890 dollar , we only have gdp in 1992 dollar. Dollar values have dropped about 15 times from 1890 to 1992.
You can look at these reference to get your own GDP figure for China in 1890:
http://ehsanz.econ.usyd.edu.au/papers/Deng.pdf for China Economy in Silver.
http://www.ucl.ac.uk/~uctpnpa/growth.pdf for U.S GDP in 1992 dollar
http://www.ellensplace.net/hcg_fac8.html for silver price in dollar.