Story TELLING THROUGH Data Visualization

Hi,
In the course,Story TELLING THROUGH Data Visualization ( Mission :Improving plot aesthetics) ,screen no. 4 (Visualizing gender gap) , how the % for men Biology degrees calculated by directly subtracting women’s column by 100. How it is possible.

[‘Biology’] column is provided in %. For example, you will find 71 instead of 0.71 as value in the column.
You can simply do ‘100 - df[‘Biology]’ to return %value associated with men.