1980 KZ750 Twin spark plug?

So I just recently pulled the plugs in my 750 twin. The ngk part number on the plug is B8ES. After searching the Web I've seen that the plug people normally run is a B6ES. What is the difference? And do these plugs come pre gapped or what is the recommended gap?

The B6ES is a hotter plug than B8ES. The B8ES is usually run in the four cylinder engines but the 750 twin specs the hotter B6ES which prevents fouling.

Correct gap is 7 - 8 mm which is .028 - .032".

So I imagine that the number encrypted in the part number indicates the heat range. If that being the case, advance auto website says the B8ES plus 8s an 8 heat range opposed to the B6ES being a 6. Wouldn't the B8 be the hotter plug then?

I am pretty sure that the B6ES is hotter than B7 and the B7 is hotter than B8. They get hotter as the number reduces.