You will find much more information about Amazon Capsules posting your question at the Forums. There are more experts at the forums who don't frequent the Q&A. Post it at HubPages Community → Getting Help from the HubPages Community. There you will meet people who use them 'Successfully'.
Anyway . . . I rarely use Amazon capsules. But, I don't have many Hubs anymore. Amazon capsule usage is restricted much more in the recent year. Especially with Hubs going to Niche sites. I see at your profile you have Hubs at the Niche Sites like Calorie Bee.com. Hooray!!!!!!!!
That is a very good thing because more traffic will arrive from being there. But, used incorrectly the Hub has a good chance of not being featured or going to a Niche Site. Over usage on a singular Hub is very much frowned upon. Recommended is no more than two. One is preferred IF used.
*** Amazon capsules have to be 'Directly' related to the title and the content
*** Amazon capsules have to have 300 words describing, answering why recommended, and is best with personal experience
So, if an article is about frying chicken then a capsule for a crock pot or a general cook book would not be be acceptable. One for a iron fry pan may be if related to the title, content, with those 300 words, and hopefully personal experience.
Footnote: Capsules for books are the hardest to do IMHO
I hope that helps a little . . .