Hello! I'm Jen, and I'd be happy to help you out with this issue.
Please check if both displays have the same scaling settings. Go to Windows Settings > System > Display > Scale and Layout > Scale and select whatever percentage you want for both displays and then restart the system to save the changes.
If the problem persists, it could be that their resolution doesn't match. Please make sure to match the resolution of the monitor as closely as possible. Let me know how it goes. Thank you.
I hope this information helps. If you have any questions, please let me know and I'll be glad to assist you further.
Best Regards!
Jen :)