Support Board

In this case the "rollover" is applied at the begining of the time period and not at the end as it should be in a rollover function, so it makes no sense.
All the above to say that the "Number of Days to Calculate" input should be eliminated because in a real rollover function this input should equal to "Time Period Lenght" (i.e. "Time Period Lenght"="Number of Days to Calculate"), so it's not necessary and furthermore if you set it with a value different from "Time Period Lenght" the plotted function it's not a rollover function.