Tree: 1 (root) has children 2 and 3. Node 2 has child 4. DFS walk: Enter 1 (tin[1]=0, timer becomes 1), enter 2 (tin[2]=1, timer becomes 2), enter 4 (tin[4]=2, timer becomes 3), exit 4 (tout[4]=3), exit 2 (tout[2]=3), enter 3 (tin[3]=3, timer becomes 4), exit 3 (tout[3]=4), exit 1 (tout[1]=4).
Subtree of 2 covers [1,3). Subtree of 1 covers [0,4). Notice tin values are unique while tout values repeat (tout[4]=tout[2]=3).