How do I limit the max size of a repository?

Such as title,how do I limit the max size of a repository?

It is not implemented yet, you can track progress here Repository Size Limit · Issue #3658 · go-gitea/gitea · GitHub.

You can limit number of repositories, see [repository] MAX_CREATION_LIMIT, [repository] ALLOW_FORK_WITHOUT_MAXIMUM_LIMIT, and related limits Config Cheat Sheet