This tells you nothing about number of people that would die as a result. Remember what happened to global trade when 1 ship was stuck in Suesz?

It takes a couple dozen nukes to destroy all large-scale deepwater ports in the world. Global Trade is crippled. UK and Japan depend on food imports, so people there starve.

It only takes a couple dozen nukes to destroy most oil refining capacity in the world. Czech republic has enough gas to last 6 days

I've played with the nuke map occasionally for years, though I've never taken it too seriously in terms of estimating realistic damage. I'm not sure what targets would be hit, and by which bombs, and even then, the circles don't provide a holistic, long-term description of damage. But it is a lot of fun.