Dark Side Territory Battle - P6 Special Mission

I got Imperial Probe Droid, Starck, and Veers to 7*. I didn’t realize that seven 7* empire toons were required for the special mission until after deploying toons in platoons and other combat missions. I was not able to enter the special mission because of this requirement. The special mission only requires five Empire toons, included the three mentioned earlier. Why are seven required when we only need five?