I am trying to define seismic loads per IBC 2012 with the following command:

DEFINE IBC 2012
SS 0.162 S1 0.055 RX 2 RZ 2 I 1.5 TL 4 SCLASS 4 KX 0.75 KZ 0.75

However, I get an error message when STAAD reads the file saying the SDS parameter is defined incorrectly.  I'm assuming it is referring to the design spectral response acceleration parameter at short periods for SDS.  In section 5.31.2.16 of STAAD.Pro Help pages, it doesn't say that the SDS parameter can be defined directly though.  I don't get an error message when using the same definition above in STAAD.Pro Build 20.0 (except that you have to define K for both directions instead of KX and KZ).  

Can you tell me what the correct procedure is for defining seismic loads per IBC 2012 when using STAAD.Pro Build 21?