GRE Quant Concept Series Mistake?

on the GRE Quant Concept Series part 2 of Fractions Decimals, Percents, and ratios at 35:31. Greg said that -15 to 30 presents a percent increase of what? The solution he said was 100 increase but shouldn’t it be a percent increase of 300 since its from -15 to 30?

I think the “-” wasn’t supposed to be “-30” - it is like a bullet point instead.

ah i see that would make more sense