From a superstonk thread explains short volume, seems credible...
"to clarify: the dark pools did not collapse. DIX printed a 41.8% because retail got rug pulled.A high/big DIX value is usually consistent with future price appreciation, and a low/small DIX value is typically a bearish indication, though repeated data prints to indicate trend are going to be more reliable than a single print, just from a data perspective.
The low print from Friday is just a confirmation that the selloff was mostly absorbed by retail. A large reason for why Friday dumped at all was because of the unstable options activity on NVDA: lots of call options got sold-to-close, a bunch of put options got purchased-to-open, and a bunch of OTM call options got sold-to-open. In aggregate, this created more selling pressure than there was demand to purchase shares of the underlying (NVDA, SPY, etc.) and so the market dumped in dramatic fashion.
GME has a DIX too, it's usually very large (heh. nice.), and you can see it for yourselves by looking up the short volume off exchange (a public source of this data is at https://chartexchange.com/symbol/nyse-gme/short-volume/ )
But there's a few problems with these data:
most of the posts about GME short volume that I see on this and other subs are written in a rage-baity way that completely misunderstands what these numbers even mean. High short volume off-exchange is a signal that institutions are buying shares of the underlying, so if you're a GME bull, you actually want to see big DIX / high short volume off exchange. Most people I've seen get mad at this because they don't know wtf they're talking about. CBOE put their short volume data behind a hefty paywall many months ago, and instead of reporting every day, they report at the end of the month. This makes it more difficult to use DIX on individual equities to try to determine market behavior. Fractional shares, for some reason, get reported as whole shares when it comes to reporting volume. All of these things dramatically muddies up the waters for trying to get a clear signal for what the market is doing"