Scale Throughout the Day sets the percentage of the daily budget that applies in each time slot, and the system adjusts automatically every hour. Ready-made presets are available: Morning Peak, Night Peak, and Gradual. You can also build your own schedule with the + Add time button. Before the first time slot you set, the campaign runs at 30% of the budget (or at the lowest percentage you set, if that's lower). This keeps Meta from spending the whole budget before your peak time. A visual timeline in the form shows the resulting budget curve across the day.