Can you share a sample worksheet?
Wont be able to share it as it has some sensitive info
Can you change the reference line to Scope: Entire Table?
You can then click on it and format it to align to top (imagine that's desired).
Unfortunately you can't really format the tooltip on the reference line - this is something that's been highly requested! You could use a parameter instead as then it's nice and clean...but would require writing something to download your workbook, change your parameter for you, and re-publish (aka probably not worth it).