Understanding Ratings

Thank you to pricklepants (who used to work in the entertainment industry) for sending this nice link that expertly and clearly describes ratings for those (like myself) who are constantly confused by it all.

Do you know if watching the show on Hulu the following day counts toward ratings? 
You know what? I’m not actually positive about that! I think it does? But if it does, I wouldn’t think it would account for much. Just because the ads for something like Hulu and actual TV are totally different.

Is there someone out there who could answer this better than I can? :)