Thank you for the opportunity to help you with your question!
In this case the elevator and the person are initially at rest at a higher floor.Here the acceleration is negative.It means that the elevator speeds down in the downward direction towards a lower floor.The inertia of the person prefer to stay at rest ,so the elevator floor and the scale effevtively drop out a little bit from underneath the person as the elevator accelerated down.
The free body diagram is shown below:-
Weight of the man=mg=77*9.81 =755.37N
I hope this would help you,but if you have any doubt regarding this,you can surely ask.