In Chapter twenty- five Tris went through Four's fear landscape with Four. Four seemed to be freaking out a lot but Tris was able to help him through without herself freaking out. Four has four fears so that's why they call him Four. Tris found out that Four's real name was Tobias and that he was from Abnegation just like Tris.
Why does Tris just do Four's fear landscape calmly? Four had four fears but how many fears does Tris have?