Surely you remember writing 'H T U' (for hundred, tens and units) above the columns in infants school?
Anything to the LEFT of the decimal point is simply sticking to those rules. So, in Q8, the 2 is in the 'hundreds' column, the 7 is in the 'tens' column and the 1 is in the 'units' column.
Columns to the RIGHT of the decimal point follow the same patter (i.e. you divide by 10 to go from the value of one column to the value of the one to the right of it). So, in Q7, the 4 is in the 'tenths' column and the 1 is in the 'hundredths' column.