GitHub commit graph showing weird behavior?

I have been an active developer for the majority of last year, and my contribution graph has been very active. However recently GitHub contribution amounts have started fluctuating on my page. I had a good ~6.5K commits about a month ago, but now they were reduced to 5K ish on my profile. I thought the profile was having a glitch so I didn’t explore but just now roughly 500 commits were discarded from the contribution amount on my profile. Any reason as to why this is happening?

Repositories you have previously committed to may have been deleted, which would result in a loss of those commits.

Deleting branches will discard the commits in them if they’re not reachable from any other branch. (And unlike a repo on your PC, github is very prompt about this.)

Rebasing can easily create duplicates of whole chains of commits.

If you have a new dev branch, then make a temporary branch from it that you use to rebase & fast-forward into your master branch, you get double credit for your commits until you delete the dev branch.