Automatic Version History in SharePoint Online, hourly, daily and weekly versions?

I am considering on enabling the automatic setting for version limits in SharePoint Online, however, is still unclear to me, how the algorithm identifies hourly, daily and weekly versions. From the documentation this is what it says about:

• All versions created within 500 count limit in first 30 days.
• Hourly versions (versions created at the top of the hour) between 30 to 60 day period.
• Daily versions (versions created at the beginning of each day) between 60 to 180 day period.
• Weekly versions (versions created at the beginning of the week) beyond 180 days or more are available indefinitely until the maximum 500 count limit has reached.

My question is, what is considered "at the top of the hour" or "beginning of each day/week"? Does it mean that only versions created at 09:00, 10:00, 11:00 will be kept? What if the version has been created at 09:03 or 09:46? Additionally, what if there are several versions created within the same time frame, which one will keep?

I hope my question is clear enough.

Thank you so much in advance.