how does convex charge for chef tokens?

❔Advice

I have built five projects for practising Convex use with a Nextjs app, and there is hardly any activity on any of these as I was learning and was not able to complete the projects. I have got a bill for payment from Convex for 51,900 Chef tokens. I do not understand how these Chef tokens have been created as there is hardly any usage. Can anybody suggest what I should do?