If a creature spawns more creatures during the combat, how does it affect the challenge rating? [duplicate]

I’m trying to balance a combat encounter for my players (in this example 5th lvl, 10 characters). I want to use the Sword Wraith Commander (SWC) (MTF, p. 241). The SWC has a CR of 8 but with its call to honor ability, it can summon 1d4+1 sword wraith worriors (SWW) which have a CR of 3 each. One CR 8 monster is rated as a trivial combat encounter but adding five CR 3 monsters makes it deadly.

This raises the question: Is the ability to summon up to five CR 3 monsters included in the CR 8 rating (meaning the total combat with the SWC and up to 5 SWW has a CR of 8) or do we count the CR’s independently?