OK,I thought I was doing this right but a player made some comments and now I'm second guessing myself.
Example: page 210 making range attacks while engaged. So a player in engaged with NPC A he is using a light ranged weapon and wants to shot at NPC B in Medium (average difficulty 2P) the chart says +1 difficulty so I told him to use 3 purple dice (hard difficulty).
The player mentioned it says upgrade difficulty so it should be 1 purple and 1 challenge dice (upgrading the difficulty).
Looking at page 21 it states normally you don't add additional dice once the difficulty is set. So, when do you increase difficulty by adding a dice or upgrade to challenge dice?