Tree: 1−2, 1−3, 3−4, 3−5. Five nodes total. Start at node 1. Its subtrees have sizes 1 (node 2) and 3 (rooted at 3). Node 3's subtree exceeds 5/2=2.5, so move to node 3. From node 3, its children 4 and 5 each have size 1, and the parent direction has size 2 (nodes 1 and 2).
No component exceeds 2.5. Node 3 is the centroid. You walked from root to centroid in one step. The algorithm terminated quickly because the tree is small and well-balanced.