What is Microsoft 365 Message You are using more licenses on your trial than what you will purchase once the free trial ends.

You're using more licenses on your trial than what you will purchase once the free trial ends. Increase the license quantity for your paid subscription.

You will see the above warning message in your Microsoft 365 Admin Center if you are using a trial of Microsoft 365 Business Plan and you have added/assigned more user licenses than what you are planning to get billed for when the trial ends.

On Microsoft 365 Business Basic Trial you are offered with 25 licenses. Under Paid subscription I have only one License, but I have created two users and hence the warning.

Based on what your plans are you can adjust the number of licenses you want to purchase under Paid subscription -> Add more licenses or Remove licenses

Found this helpful:
Understand subscriptions and licenses in Microsoft 365 for business
https://learn.microsoft.com/en-us/microsoft-365/commerce/licenses/subscriptions-and-licenses?view=o365-worldwide