In order to get the results shown, the calculations must be done incorrectly. Ordinarily, instructions to round to a particular precision should be applied only to the final result(s). Here, you are expected to round every intermediate result. (This is generally considered to be WRONG!)
The numbers in the column
are simply the squares of the numbers in the column to its left. Round the squares to tenths. Their sum should be the value indicated in the bottom row.
The standard deviation is the square root of the variance,
√(99667.2) ≈ 315.7
The numbers in the column
The standard deviation is the square root of the variance,
√(99667.2) ≈ 315.7