New Pull Request has message "This branch has conflicts that must be resolved" but no conflicts exist

Yep beginner here.

Before I clicked “Create Pull Request” I carefully checked the differences between ‘Main Branch’ and ‘First-branch’ and they were as expected (checked code line by code line). Now in the newly created Pull Request I have a message “This branch has conflicts that must be resolved”.

I click on ‘web editor’ and of the 5 or so differences that I saw before creating the pull request, there is a ‘problem’ highlighted thus.

<<<<<<< First-branch
# Changes Tue 12:39

=======
>>>>>>> main

# Changes Tue 12:39’ is an expected difference between my 2 branches.

What is the problem?