The billing cycle is monthly, so you will be charged after 30 days, but if you're using pay-as-you-go and you remove all your infrastructure after those 2 days of use, you should only be charged for those 2 days once you complete the billing cycle. This should explain it a little bit better pay-as-you-go.
You can also have a look to this article which might help you understand most things related to billing and costs. Describe factors that can affect costs in Azure