This means you will not be able to create more than 7 days between running your irrigation system.
So here are some conversions into a limited 7 day schedule.
If the calculator says 3 or 4 days between waterings: Choose two different days of the week at least 3 days apart.
If the calculator says 5 days between waterings: Choose two different days of the week at least 3 days apart. But reduce the minutes per cycle in half.
If the calculator says 6 of 7 days between waterings: Choose 1 particular day.
If the calculator says 10 to 14 days between waterings: Choose 1 particular day but cut the minutes per cycle in half.