Question about Browser Caching in Hummingbird related to Expiry

I am working on my Hummingbird settings to improve my site speed. When I am in Browser Caching I set the Expiry to the recommended 8 days on each one. When I click Re-check Expiry it shows that none of them are at 8 days despite that being the one I picked from the drop down menu. I have very limited tech knowledge...so please be patient with me!