Actually i had that first and call it "non-earnings median implied volatility" and the column label is "NE. M. IV".
See https://steadyoptions.com/forums/forum/topic/3885-rv-charts-volatilityhqcom-official-thread/?do=findComment&comment=83524.
What do you mean exactly ? Do you want the actual strike of the calendar ? Or the absolute difference between the stock price and the calendar strike ? Or the relative difference between the stock price and the calendar strike ?