You didn't say how large of a nitrous shot but for a rough generalization these are 2 steps colder than a Champion 12 series https://www.ngk.com/product.aspx?zpid=10043
2-1/2 steps colder than a Champion 12 series. https://www.ngk.com/product.aspx?zpid=10044
And these are three steps colder https://www.ngk.com/product.aspx?zpid=45385
I say "generalization" because whenever I've cross referenced NGK's heat ranges to other makes they tend to have a broader range. However, that's also been the projected tip plugs.
