Store Reminder for Recurring Event using RRULE in MySQL and PHP

I am building a custom events system with reminder for event if user wants to create. If you have repeating event that is like

Event A repeats every day at 10AM starting on June 20, 2020

I have used RRULE to store and retrieve the repeating events. Now, User selected to reminder like

every day before 15 minutes of event time.

How should I store this event, retrieve and show notification to user.

via Chebli Mohamed