Please help! Can someone explain why I pay $0 for my meds? Kaiser HMO

Disclaimer: Insurance confuses the hell out of me so maybe the answer is obvious?

NORTHERN CALIFORNIA. KAISER HMO – idk what the plan is, but I think it’s called Platinum? Currently at $160.97/$1500 MAX OOP.

I was looking into whether or not my plan covers a certain medication. I use the drug estimate cost tool Kaiser links you to (MedImpact) and noticed that my usual prescriptions were priced anywhere between $5-$30. All of them also have a message saying “The requested product is not covered by your plan. (ref. 400)~”. However, when I pick up these prescriptions, I pay $0.

Under claims history, it also says “MEMBER SHARE/PLAN SHARE: $14.79 / $0” (used my shampoo as an example)

On the benefit summary page on Kaiser it also says I’m supposed to pay $100 copay and yet I haven’t gotten one bill. My billing page say I owe $0.

Obviously I am not complaining, but it’s just confusing to me and I don’t want to bother asking my PCP for a certain med if it’s not even covered on my plan’s formulary which I also admittedly don’t understand lol.. Like if it’s on the formulary, does that even necessarily mean my plan covers it?