Why does the report generation on Matomo Cloud take a large amount of time?

I’m still new to Matomo and wondering why the report generation on our Matomo Cloud takes so long. The Matomo website states that by default reports are generated every 15 minutes. In my experience the report generation takes several hours. Is there something wrong or does the Matomo Cloud version have much larger update intervals than 15 minutes?

Apparently the report generation for today’s data happens every 6 hours for Matomo Cloud.