銷售額的增長%, 為什麼逐年遞減?

If this is for sales, your new boss may consider the sales of a specific product rather than the total sales.
If this is for the gross profit, the gross profit may reduced yearly even the sales figures are increasing yearly. That is to say, the cost of purchases or the cost of goods sold are increasing much greater than the sales.
To avoid misunderstanding, you have to check it with your boss as far as the viewpoints are concerned.

你未列出成本，睇你數字肯定成本同樣大幅增長。