These levels are based on price around earnings day. I have implemented support for 2 calculation modes:
Mode 1: Level = (low of 1 day prior to earnings + high of 1 day after earnings) / 2.0
Mode 2: Level = (hl2 of 1 day prior to earnings + hl2 of 1 day after earnings + close from earnings day) / 3.0
Chart above shows "Mode 1". Mode can be changed via options...