PWN The SAT Book – Volume Chapter – Question 10

PWN The SAT Book – Volume Chapter – Question 10

I am having hard time understanding how to differentiate if the question wants you to answer in feet or inches, since the last part asks : “How much does the water level rise, “in inches”, when Priya places the stone into the tank.

But the answer is 0.125 inches instead of 216 inches.

Shouldn’t the water displaced by a cube of sides 6 inches be 216 inches instead of 0.125 inches ?

Thanks