Each account can hold 30 license keys, and you can add more accounts by creating a different email address (doesn't have to be a Microsoft email).
How do I know how many Windows Licenses I have?
The most you can do is to go to account.microsoft.com/devices to see a list of all the devices associated with your Microsoft account.
What is the maximum number of Office Licenses I can activate using the same Microsoft account?
Two Microsoft Office License In One Microsoft Account.