Why was Delhi's official AQI 494 but international monitor said 1,600?

Delhi's AQI was recorded at 494 by CPCB on Monday but international monitor IQAir reported AQI levels above 1,600. Discrepancy arises because India's AQI scale is capped at 500, with anything beyond this classified as "severe plus", an official said. International monitors lack upper limit and report values exceeding 500. Moreover, IQAir's AQI is sensor-based while Indian index is analyser-based.