Some units are listed as taking up a single choice, for example 1-2 Chaos Spawn can be taken as a single Rare choice. As implied, this means that these two units count only as one choice. So a Warriors of Chaos army of 2,000 points could contain between 1 and 4 Chaos Spawn. If it included 1 or 2, they would count as a single Rare choice; if it included 3 or 4 they would count as two Rare choices.