Free space of unmerged deleted branches

Hello everyone,

In one of my repositories someone pushed over 2 GB of data in a separate branch. Of course I didn’t merge it and instead deleted that branch on GitLab (agreeing to the pop up message of possible data loss). When I clone the repo I can not find those files in the history, which is good. However the usage quotas still show that the repository is over 2 GB and if I export the project I can see that it’s huge.
How can I let GitLab know that the data from deleted branch should be freed? Is there an easy way?

I tried to run Housekeeping in the project settings but it didn’t resolve the issue.