Set quantize factor in WIC

I am trying to Repalce the encoder module of a application with my own Encoder which use WIC. and the old one seems set the Quantize factor to 90 (i dont know what happen in there, i just have dlls only). Now i have to set quantize factor too but i dontknow how. is there any way to set that value like passing some value, or am i need to implement Quintize tabel and calclate the factor. I sow there is a way to set image quality (which 0 to 1) when initializing the encoder,

PROPBAG2::pstrName = L"ImageQuality";

dose that affect to the quantization?

the question looks like silly but google didn't help me. can anyone please help me.