Question

I am having trouble understanding the pricing of Google App Engine.
Here is the price:
https://cloud.google.com/pricing/

As It says, for paid plan, it costs $0.08 / hour for On-Demand Front End Instances. What does that mean?

1. It means if your app scales to 5 instances for 10 hours, you only
   have to pay $0.08 * 10 = $0.8. (No matter how many instances you
   need, you pay by hours).
2. It means if your app scales to 5 instances for 10 hours, you have to
   pay $0.08 * 5 * 10 = $4

Which way of understanding is correct?

Answer 1

the second one is right.
+ you pay a few cents for every instance start (don’t remember how much)
and you have 28 instance hours free per day.