Help with a Hickok TV-7D/U setting line voltage

I just bought this Hickok TV-&D/U tester in mint condition and sort of found the settings for 6550 tubes. Now setting line voltage, holding the line voltage and adjusting on scale, directions say to align with line test mark, I see a horizontal line from 40-80 just under scale with a vertical line I beleive that is at 60, where do you set it at? I presume the verticle line of 60 because changing this changes the overal result? any help would be so greatly appreciated, military instructions are vague. how do I properly use this tester for 6550 and kt88 along with several others like 12ax7 tubes. any help is appreciated allot, thanks