Battle For Gondor Setup Question

By Gamer, in War of the Ring

The setup for the Battle for Gondor indicates that you use 8 Nazgûl figures. Shouldn't the quantity be 7 since you can also have both the Witch-king and Gothmog minions in play?

I don't understand. Why would the presence of the Witch-king and Gothmog reduce the number of Nazgul available?

Gothmog isn´t nasgul

My mistake. For some reason I thought Gothmog was a Nazgûl. Thanks for the replies.