Any questions? Let's see if we can help you
“[...] When the total of tokens is equal to or greater than the value of your Wounds attribute (W), one of your troops will be taken out of combat. Immediately remove the model from the battlefield and remove from its game profile as many damage tokens as its W value”.
When removing troops from a unit engaged in combat, you may not remove troops that cause your unit to no longer be engaged with the unit that has inflicted damage. If necessary, exchange the leading unit with another troop of the unit before removing it.