Taking the lead from ASCE 7, the vertical static seismic component would be 20 percent of the short term (0.2 sec) response to the ground motion. This value - 0.2*SDS - is used in the ASCE 7 load set considering response to seismic load. This is what we produce in the static seismic wizard.
Note that, currently, the wizard will also adjust the g loads by the 0.7 factor to account for the differences between the load resistance factor design method of ASCE 7 and the allowable stress design method of the piping codes.