The usage estimate in the web application of proton drive is still buggy. It shows much higher than what I have in my drive. I saw a reddit post about this that was posted 3 years ago, I don't know if it is already fixed and is an issue with my side of the application.

https://www.reddit.com/r/ProtonMail/comments/ww5wws/i_question_the_accuracy_of_protondrives/