Currently the reminders triggered in the client machines by the SPE have a default setting (50 mins) and interval (5 mins, 10 mins, 30 mins, 1 hour). There is no way of altering those in the product, neither via GPO.
An enhancement request (TF00644113) has been created detailing the feature: "The ability to alter the interval and/or default setting of the notifications presented via the SPE (Remind me in:). “
The product team will evaluate the request and this feature may become available on a future release of the product.
Please refer to this article for updates or contact support referencing the Enhancement Request ID: TF00644113.