Hello again Anna-Mariya,
This is a great question.
Based on that message, it seems like your site might actually be installed as part of a multisite server. The message is popping up because you have a personal license (not a multisite license).
I would recommend reading the following: https://theeventscalendar.com/knowledgebase/multisite-license/
To summarize, it is totally cool to use a personal license on a single site located on a multisite installation. However, the drawback is that automatic updates will not be available. You will have to perform them manually.
Let me know if that helps.
Have a great day!
Geoff B.