…….if you put a 4 hour setting in….then the next time the song comes up, 4 days or 3 weeks later, depending on the turnover of the category, M1 will make sure it doesn’t re-schedule within 4 hours of where it was previously scheduled/last time.
now, the main thing about such a thing is the rotation pattern of the category itself should be acceptable, according to what you see on the category Rotation Chart. the category should be arranged so a song wouldn’t naturally come up at about the same time, next play. but if you do a lot of messing around, substituting and replacing songs that were scheduled by M1, you get to dropping songs into a schedule well outside their normal pattern. like, if a song schedules Mid-day and is next normally going to come up in evenings, in regular rotation, you might drop the song into the PM drive slot manually….thus the pattern is now odd for that song and maybe the next time it comes up, it happens to be in PM drive (which might be normal, had you not done the manual schedule). So the Previous Play rule will at least ensure it doesn’t get automatically scheduled two successive times in PM Drive.