Hey Kevin! I can see why there may be some confusion here. So I'll help clear it up:
Your billing date is on the 8th of every month. This month, you added a $20 credit pre-emptively to your account on the 3rd, which just sat on your account balance.
When you were then billed later on the 9th (due to the time change, and using a UTC timezone for billing, it bumped it up to the next day), it pulled from your account balance credit. So your card wasn't charged at all, and you still have $6.01 left over on your account balance to help partially pay for next month's bill :)