I think it's showing how much those things are being used. For example, JAVA is being used 7.7% out of the total amount. The total amount is all of the percents added so : 30.8+30.8+15.4+7.7+7.7+7.7=100.1. About 100. JAVA is 7.7 out of 100. JS is 30.8 out of 100. CSS is 15.4 out of 100. The others the same way
I hoped I helped!