It really will be telling.
Once again, I'd take this with a grain of salt, but I've seen two numbers tossed around for the amount of Hypersonic missiles that Russia has; 5 and 50. If they really only have 5, they would have just used 20% of their stockpile for one target... in Ukraine. I think that number is unlikely, but even still, if they only have 50 that a not so small percentage for Ukraine.
If we see more being used liberally, I don't think it would be outside the realm of possibility to assume that either China would be providing them with the materials to create more (given their current trade limitations) or that they really are running out of supplies. Given that they're one of the newest conventional weapons in the public eye right now, I find it hard to believe they would have a 'fuck you' amount of these to just throw around willy-nilly as they're probably rather costly to create.