Is there a slight math error here, or not?
"EG, at sea level with a measured pressure of 993 Hpa and a temperature of plus 25 degrees C - difference from 1013 is 20 Hpa x 30 ft = 600 ft PA.
"At 600 ft PA in ICAO, the temp should be plus 14 degrees (or close enough) giving a difference between measured T and ICAO T of 9 degrees x 120 = 1080 ft, added to the 600 ft PA = 1680 ft DA."
25 - 14 = 11
11 x 120 = 1320
1320 + 600 = 1920 ft DA