The CNAME for each domain/weblog would point to
regardless of which individual blog the domain is to be mapped. You select which blog to map the domain in TypePad only, not at the domain registrar, so the CNAME Record will be the *same* for any domains mapped to your TypePad account.
When you go through the domain mapping wizard under Account > Domain Mapping, the last step is to choose either your whole account (Main Site) or just one blog or album. At Step 3, you will choose the specific blog to map the domain.
More information is available in the Setting Up Domain Mapping article here:
If you need any further help with this, please let us know or feel free to open a Help ticket from your account and we'll get you set up.
Thanks so much,