What does it mean by "Usage must be reasonable"?

https://preview.redd.it/89jmfceor66e1.png?width=590&format=png&auto=webp&s=2dd4d75e53cea5509feee5ee323c02bdbc6cbc95

What is exactly "Usage must be reasonable"? I'm considering buying the Pro model for my data analysis / analytics tasks and for my own fun. I'm sure that the former is a reasonable use, but what about the latter? Does that mean that I cannot use ChatGPT for my own fun? To what extent is the usage "reasonable"?