An integer that indicates the number of periods the product discount is available.
- iOS 11.2+
- macOS 10.13.2+
- Mac Catalyst 13.0+
- tvOS 11.2+
- watchOS 6.2+
A product discount may be available for one or more periods. The period, defined in
subscription, is a set number of days, weeks, months, or years.
The total length of time that a product discount is available is calculated by multiplying the
number by the period.
Note that the discount period is independent of the product subscription period.