Hi Sara,
I think what you're seeing is the image description from hovering over where the checkmark will display when an email is opened. That description is displayed if you hover a checkmark or non-checkmark for the Open column. For the Click having a check without one for Open, this can happen frequently when a Lead does not download images for the Email as the Open activity for Sales Emails relies on the tracking pixel the same way Marketing emails from Marketo do. If you're not including any images that would entice a Lead to download images for your Sales Email then they could skip downloading images but still click on the tracked link.