Branch merge recognition error

Even though the protected feature branch A has been merged into main,
the changes from feature A are also present in main.

However, when accessing the branches section, the branch status shows
“25 commits behind main, 1 commit ahead” message.

Attempting to delete it results in the message:
“This branch hasn’t been merged into main. To avoid data loss, consider merging this branch before deleting it.”

I’m curious why it’s showing like this despite the merge. Is it just a simple error?