Discount codes for courses and bundles.
Two kinds of discount
A discount is either a percentage or a fixed amount. That choice can be changed after the code has been used — but past purchases were recorded on the terms of their own moment and do not change.
Two different limits
The total limit says how many times the code can be used altogether. The per-user limit says how many times one person can use it.
Both are optional. With neither set, the code works indefinitely.
The date range is separate from being enabled
A code can have a start and end date, and separately be enabled or disabled.
So a code that "does not work" usually has one of two reasons: it is disabled, or its start date has not arrived.
Disabling does not claw anything back
Disabling a code stops new uses. Enrolments already made with it are untouched.