I've never submitted anything to the Asset library and the docs are sort of strangely worded, but... I assume that it wants the hash of the commit that should be retrieved from GitHub. Looking at the provided GitHub link, I think that'd be this:
Near the top of your GitHub project page, you'll see this:
newold3 committed 863ac17 2 hours ago
If you click that short hash (it's a link) that leads to a page that has the full hash in the URL (which is what I copied above). The same hash value is also listed in the page itself.
Again, not 100% sure, but I think that's what you want...