If frequency is non-zero, the service will be ignored if it is active or not by days of the week according to the day of entry.
An example of how these parameters would work would be the following:
If we have frequency=2 and no. of days to start=0 and if a booking comes in on Monday, the service would run on Wednesday, Friday, Sunday, Tuesday, etc.
If the number of days was 1 instead of 0, the service would run on Tuesday, Thursday, Saturday, Monday, etc.