Is there any limit of events for subscribing a feed from API to outlook calendar?

I created an API that fetches iCalendar events and subscribed to this API from the Outlook calendar. It's working fine for a smaller number of events. All the events that are fetched from the API are displayed. But, when I fetch a larger number of events (around 15,000 events), the Outlook calendar only shows a few events.

When I uploaded an ICS file with a larger number of events to the Outlook calendar, all the events were displayed. But, when I tried with the API, it does not show all events.

I searched for if there is any exact limit to the number of events. Google calendar has a limitation mentioned, that is up to 1MB file size. But I was unable to find any limitations for Outlook calendar. Really helpful if someone knows if there is any limit there.

This is the link[1]  to the large calendar

This is the link[2] to the small calendar (This works fine)