Huh? Where are you getting this number from?

This missile wasn't just a nuclear-capable missile with a normal warhead. This missile had no warhead, unless you count a lump of concrete ballast as a warhead. That's what made this so weird, Russia either launched a Kh-55 as a kinetic missile (+ whatever fuel is left behind), which would be really pathetic if true. Or they launched it as a test for how an actual nuclear armed one might go.

Or what I think might be most likely, perhaps this was a training exercise for the pilot, and they thought "why not fire it at Ukraine anyway". Which is still dangerous because they still got the data.

Or it's a pathetic feint. Or I've also heard it suggested that perhaps it was a distraction attempt, only problem is they barely launched much of an attack on that night.

So I don't know where you're getting the 500-1000lbs of TNT from?

Edit: the actual warheads are:

Nuclear: 5 to 150 kilotonnes of TNT

Conventional: 1000lbs HE (nice guess), or a few cluster bomb variants

Again so the Kh-55 can take a conventional warhead. So why the hell was a dummy nuke launched?