Retention time/period for real-time notifications of auto-renewal subscriptions

how many times does apple try to send notifications for auto-renewal subscriptions if the listening service(webhook) is down for sometime.

And also for how long? like a day, 2 days or else?

Send HTTP

50x

or

40x

to have the App Store retry the notification if the post was not successful. The App Store makes several attempts to retry the notification over a period of time but eventually stops after continued failed attempts.

They have not specified it anywhere.