How are transaction fees by brokerages calculated?

Recently I participated in the dbs digiportfolio and they have a flat 0.75% annual fee. POEM on the other hand charge a one time 0.32% fee per transaction (min 25) and assuming rebalancing is done annually, the 0.32% allows for trading of multiple stocks or only for a single stock? I.e if I want to sell stock A and buy stock B for the interest of rebalancing, is this counted as one or two transactions? If it's counted as two transaction, won't rebalancing through brokerage be a costly affair?