Finding The Parking Floor

What was the given data? 

The sentence 'The first one to get out is Harold.' suggests that the Harold leaves the lift at the 1st floor.

Similarly, the sentence - 'Simon stays in the lift for the longest.' suggests that Simon leaves he lift at the 6th floor.

Next, sentence - 'Debra leaves after Tracy who gets out at the third floor' suggests Debra leaves the lift at the 3rd floor.

Clearly, the sentence - 'Sia gets out before Peter but after Tracy.' suggests that Sia leaves the lift at the 4th floor.

Also, it is clear that Debra leaves the lift at the 2nd floor and Peter at the 5th floor.

Summary -

Harold leaves at the first floor.

Debra leaves at the second floor.

Tracy leaves at the third floor.

Sia leaves at the fourth floor.

Peter leaves at the fifth floor.

Simon leaves at the sixth floor.