The response spectrum loading represents seismic acceleration applied at the base of the structure and this dynamic loading would vibrate the structure in both directions. The nature of RSA is such that the responses are all absolute maximum responses. So you don’t need to apply it in the positive and negative direction as you would typically do for a static seismic case. You should rather define two combination loads to combine these with the gravity loads as shown below
LOAD COMB 100 DL + EL
3 1.0 4 1.0
LOAD COMB 101 DL - EL
3 1.0 4 -1.0