Pro forma is just a fancy way of saying “what the future could look like.” It is forecasting based on an increase in sales. Look at your financial statement and everything on it that is dependent on sales. In this case, let’s say COST OF GOODS SOLD (COGS) and ADMINISTRATIVE expenses both increase with sales.
If sales increased by 20%, what would our net profit be? Look at the previous page and see that COGS was 22% of sales, and your administrative expense was 3%. When increasing $90 by 20% ($108), you then figure out what 22% and 3% (COGS and administrative, respectively) of $108 are.