helping with DAX -

Hello guys , I need your help , to elaborate I included the table below 

I have gategories ( Mobile-TV-Watches) that has average shipping delay per day , 

but in fact it is not correct for me , because for example in mobile category Samsung delay is 10 days, Apple is 15 , and nokia is 10 days , but in Average shipping culumn it gives me the sum of the average 35, and not the max which should be 15

how to solve this issue 

thanks in advance