I read it as the other way around. With the variable vacation hours, if you select the minimum (12 hours) PBS would likely only give you 9 off. With the maximum, you’d only have to fly ALV-36 hours (ex. 72-36 = 36 hours you must fly; i.e. 2 18-hour trips), however no guarantees on what days you’ll have off (same as it is now, seniority depending). However you’ll never have fewer than 9 off consecutively.