Whilst it may have been operated as 3 class some days, the EK flight is sold as 2 class therefore the load factor based on the amount of seats available on sale would be, as simonwa explained, 78.5%.
This is still a pretty good figure but lets not try and fix the figures to make it look amazing as the flight is nonetheless sold as a 428 seat, 2 class 77W on a daily basis.