Why is it so easy to accidentally add a license and so difficult to correct that error (remove it)?

Hi there,

Since you have purchased this license accidentally, you can cancel it within the first 14 days of the purchase, navigate to Adobe Admin Console > Support to contact us.

Please read the 'Remove license' section in the following help document to know more: https://helpx.adobe.com/in/enterprise/using/accounts.html#Removelicenses.