I think I found an answer to this. GitHub API can be queried to get release download stats, and when I’m quickly comparing the stats of my own plugin provided by the GitHub API to Obsidian’s community-plugin-stats.json file, they seem to match, so I guess Obsidian simply uses the same API to get download stats.
Instructions on how to acess GitHub API in terminal: Finding the download count of GitHub releases – Andy Balaam's Blog
curl -s https://api.github.com/repos/andybalaam/rabbit-escape/releases | egrep '"name"|"download_count"'
(Replace andybalaam/rabbit-escape with the plugin’s repository that you want to check).
Based on this assumption, I guess that:
- If I upgrade a plugin that I’ve already downloaded, it is counted as a new installation/download, because it causes
manifest.json, main.js and styles.css to be downloaded again.
- If I install a plugin to five of my vaults, my quick test looks like the download count is increased also for every repetitive installation.