With the days used rate engine, you can:
 set how many days should be charged for on any day of the rental (“days used”)
 specify how many days Current should count up after each “days used” entry (“increment”).
Days
Days determine how many days to charge for on a particular day of the rental and how many days should be incremented between one entry and the next.
For example, if you have a ten day rental, Current will look through the list and look for a day entry for 10 and charge based on the “days used”. If there’s no entry for “day 10,” Current will look of the entry before this and calculate the charge based on the days used and increment.
Here’s how a three day week might look:
Day: 1 Days used: 1 Increment: 1
Day: 4 Days used: 3 Increment: 0
Day: 8 Days used: 4 Increment: 1
Day: 11 Days used: 6 Increment: 0
Day: 15 Days used: 7 Increment: 1
Day: 18 Days used: 9 Increment: 0
Day: 22 Days used: 10 Increment: 1
On day 1, Current will charge for 1x day and then increment by 1 for each day between day 1 and the next entry. The next entry is day 4, where Current will charge 3x days and increment by 0 for each day between day 4 and the next entry, and so on.
Options
Day type

Calendar day
The number of days to charge is based on whole days; the start & end times aren’t taken into consideration. 
24 hour clock
The number of days to charge is based on 24 hour periods; the start & end times are used to calculate rental charging.
For example, a rental that starts January 2nd at 11am and finishes on January 3rd at 9am would be considered two days rental when using “calendar day” since it falls over two whole days, and would be one day of rental because the end time is earlier than the start time.
Rental days per week
Use this option to determine whether weekend days are considered chargeable. If you do not charge for Saturday or Sunday set this to 5, otherwise leave at the default value of 7.
Leeway minutes
This option is only used when the day type is set to 24 hour clock. It adds a grace period or tolerance to the end of a rental.
For example, if a rental that starts January 2nd at 11am and finishes on January 3rd at 11:30am then the total rental period is 1 day and 30 minutes. This is considered two days of rental charge. However, if you set 60 leeway minutes then the same period would be considered one day of rental charge as 30 minutes is less than the leeway minutes.