Free for 6 months sounds like a great offer :). If you're viewing this offer in your MyRogers profile, it may be a targeted offer for your account.
Typically you should be able to see a link "(+) SEE FULL DETAILS" at the bottom of the page to read about the details of the offer. The $19.95/mo price point is for the Crave + Movies + HBO pack. Crave on it's own is $9.95 per month.