Sentence:  This column should contain the remainder after deducting the amounts for each town or ward in column 5 from those in column 4, observed that the <WSD>sum total</WSD> of column 5, when deducted from the <WSD>sum total</WSD> of column 4, is equal to the <WSD>sum total</WSD> of column 6. 
Meaning of the word marked with <WSD> tags:  Total; the result of adding a set of figures or counting a number of items.