Shouldn’t matter what burning program you use. Are you sure you’re using Shrink version 3-beta?
The analysis button will be on the main window next to “backup”. suggest doing that before doing anything else. You also get an analysis option in the back-up dialog. Same process either way, but analysis before doing anything else will give you more accurate size and compression indications. Been a while since I did Dreamcatcher, but I recall compression was in the 50-60% range, maybe slightly more.