I found the statement of the problem to be incorrect.
Concider sample input and sample output. Certainly, the square of the stadium equals 100 sq. meters, but average amount of the rain CAN NOT be 99.666, since it is calculated as total volume (or mass) of the water divided by square of the stadium. Therefore, it can not be greater that 1 mm. May be you mean TOTAL VOLUME (measured in mm^3) in your question?

That must be true. What a huge bug!! ( is it still a bug? )

I think there is nothing with volumes, but the statement is still wrong: maybe the input details are all given in millimeters - then the result is correct.

As I now understand 1 mm per minute its normal watering, but
when we have some umbrelas some water doesnt fall under ubmberlas and other part of stadium have much watering. Or what?