Highlighter tool is bonkers

Ok, I have Adobe Acrobat Pro DC. I'm trying to highlight a number on the bank feed we printed to PDF. When I take the cursor over what I want to highlight, I get this oval shape, covering like 10 lines. It's HUGE. How can I make it highlight just the one area on the file? And sometimes it becomes a combo of shapes and sizes - makes no sense whatsoever... I tried the Ctrl + e, but that only allows you to change the color and opacity - where do I go to change the height of this thing and make it a SQUARE to go around an area?