Earthquake Loading Specified in G's
Horizontal Acceleration factor (GX) 0.170
Horizontal Acceleration factor (GZ) 0.170
Vertical Acceleration factor (GY) 0.100

I understand from such information that Horizontal acceleration is 0.17*g on X direction, etc.

IMO, the information given by codes are also as fraction of "g".
For example working under UBC Zone 2B/ and Z=0.2 means to have a PGA=0.2g (see the explanation in UBC 97 1631.2) which is PGA at T=0, without taking into account soil amplifications effects.
Depending on soil amplifications and specific T, we may have PGA expressed by other coefficients as Ca=0.35, Cv=0.64 etc (in fact we have a spectrum as defined in UBC 97).
In the end of calculation we apply these coefficients to W=mass*g; this is equivalent to say we apply accelerations as Ca*g, Cv*g to the mass which is subject to earthquake load.

Best regards.