Desktop dyno question

Just got DesktopDyno 5. Figuring it out, but for those of you that have it I got a question. I have 9.5/1 compression, and Edelbrock RPM heads which list a 63cc chamber. The program only lets me put in the compression ratio, then figures out the combustion space at 98cc. Is that correct? Or since the ratio is correct does it matter?
Thanks
Author: admin