"Schedule" is where you create planned maintenance tasks. Simply record the task, such as "Oil Change", pick the interval (mileage or days) between maintenance, and select all the vehicles which should follow the scheduled task.
You'll now see all the scheduled maintenance tasks, intervals, and amount of configured vehicles. You can sort by maintenance type, interval, amount of configured vehicles, and you can search by maintenance type.
To edit a scheduled maintenance task, just click the gear.