Actually, having more commits is negligible because of the way that Git stores the snapshots behind the scenes. Specifically, it uses a content addressable key value store. So the storage is bound to the file changes irrespective of the commits.
The commits simply hold the sha of each of the files. Technically, it is a bit more complicated than that. But from an understanding of size implications and what it is bound to that mental model should get you there. It also does additional smart things in packing this key value store to store things more efficiently that also help.
If you want to start understanding more about the internals of kid and how it actually stores stuff. The Pro Git book has a Git Internals section, https://git-scm.com/book/en/v2/Git-Internals-Plumbing-and-Porcelain which is a great place to start.