Problem with large files

[3Dlunatic]

I created a repository for my Unity project on Github, and I'm using SourceTree to back it up. I enabled meta files to be visible, so those should be uploaded too. The project has a lot of large files, and SourceTree asks me if I'm sure if I want to stage these, as they're over 10MB. Of course, I click OK, I want the entire project to be saved.

However, no matter what I do, I can't get SourceTree to commit all the Unstaged files. I increased Diff file sizes too, to no avail. What should I do?