Hi @najemnikarmy
As you mentioned, you purchased item with regular license and used for one client. It means you have transferred your license to that client. It is okay and doesn’t matter what you charge.
Remember, you have transferred your license means you have no rights to use it again for other client.
If you have plan to use that theme for many clients than please purchase extended license.
** Please use clear titles in future for your questions, and edit it
Thanks