Seen on shard 3, it's possible to buy subscription token for 1Cr, the availablitity can go below 0...

That's obviously a bug, I bought more than 400 myself because my code does it automatically, and a I guess other people too.

Yes, they used to stay until their ttl expires. It's been like that for a month or so, it did not appear in the last update. Honestly, it feels more like a bug fix, since it is now consistent with how they behave in owned rooms. It simplifies a lot the defense of remote mining, which might not have been intended.