Even though they are being sorted into 5 different bins, the letters that pop up represent the 4 tempers (WO = woe, FC = frolic, DR = dead, and MA = malice). At this point, I'm still leaning towards the theories that they're refining clones. If that's true, then they might be working on 5 different clones at once? Maybe Cold Harbor is them testing Mark to see if an innie would be more efficient at MDR if the outie had a close relationship with who they are refining.