"Precisely, Ned: so that at 32 feet beneath the surface of the sea you would undergo a pressure of 97,500 lb."

Every 33 feet (10 m)  of water the pressure increases 1 ATM atmosphere of pressure . 1 ATM is equivalent to 14.696 pounds per square inch. Professor Aronnax is calculating for Ned Land the pressure he would undergo at 320 feet (100 m).

Depth   

ATM

LBS

32feet/10m

2

30

320feet/100m

10

156

3200/1000m

100

15600