Why does a forked repository show "0 Bytes Files" and "0 Bytes Storage"?

I have forked a repository, but the information that I am seeing makes me uncertain as to whether my fork includes all of the information from the original repository.

For the original repository, the “Project overview” landing page shows “3 GB Files” and “3 GB Storage”:

However, on my forked repository, the same landing page shows “0 Bytes Files” and “0 Bytes Storage”:

Why the discrepancy? Does this imply that my fork is somehow missing information from the original repository? Or is this just because the fork is sharing (e.g., via symbolic links) space with the main/original repository?

Note that the original repository does not contain any “Issues” or “Releases” that may be contributing to these file/storage counts. I realize that these would not be copied with a fork. In my case, the only space being used is for the files in the Git tree.