Confusing payments at OpenAI

Hi All,

I wanted to try GPT-4.0 and OpenAI API Keys for application development today. Therefore have just upgraded my free tier account to the paid option for GPT-4.0. Actually with doing that I assumed I would also get an access to the usage of API Keys. But it turned out, that I still need to do a separate payment for it, which I did for 5 dollars. Now I have paid in total 25 dollars for both of the services but interestingly I see that I have a limit of 23 dollars at my usage profile in platform.openai. Therefore I am a bit confused, do I have now 23 dollars worth of API tokens, if yes why it is not 25 and how does this payments are related?

Thanks in advance!!
Merve