When the Chief first calls them to the white board to discuss thier job description, he circles the title "Tactical Narcotics Team," and puts a line through "Tactical." The camera changes to Will and Martin then back to the white board. the line through the word "Tactical" has disappeared.

It can't be invisible ink because it is the same marker as he used to make the circle, and I doubt he had enough time to either erase between the letters, or erase the whole thing and re-write it. Perhaps "Tactical Narcotics Team" was written in permanent ink, but that would be highly improbable.