After reviewing the sources provided, there is no clear information on how much discount the Advil promotion offers. The first source [1] provides information about the patent status of Advil, but does not mention any promotions or discounts. The second and third sources [2][3] are the official websites for Advil and Motrin, respectively, and they both offer coupons and promotions for their products. However, the specific discounts offered are not mentioned on the websites. To find out more information about the discounts and promotions offered by Advil, it is recommended to contact their customer service or check with local retailers for current deals.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/ADVIL
[2] https://www.advil.com/offers/
[3] https://www.motrin.com/coupons