It's how long you have / how many cores etc up and running.
Up and running means built / configured, even if they are shut down!!!
The only way to stop the clock is to delete them. I just spent 3/4 hour plus reconfiguring mine.
Remember ONLY deleting can stop the $$$'s from ticking down!
That's not true with azure (but with digital ocean). Most of the costs are due to cpu usage. When my servers were shut down, nothing was billed for cpu usage, however a few cents for storage. You can look up the details in your account.
I hear you mate. The thing is, whilst my virt machines were set up doing NOTHING, I returned overnight to see the credit down a considerable amount of money. I looked up the usage details as you mention and they had somehow figured out that something deserved to be billed. I tried again by shutting down everything, and I was still billed the next night. My advice to anyone right now is to just get em setup and go for NOW.