Help - need a formula for calculating scorecard ratings

Hello, I am trying to impress a co-worker and need help assisting him with his query. He is creating a grading scorecard for his vendors, and needs to find a helpful formula that would accomplish the following:

"We want the scoring be based on % not volume of orders.

I need to calculate the percentage of orders to total orders and percentage of issues to percentage of total issues

Then have that translate into the allowable #

1% issue equal a 2% deduction or something like that


Any ideas, I have it based on volume of orders so 25 issues on 400 is 6% but if the carrier has 25 on 4000 its minimal"

I attached a sample of his scorecard.

Thanks! You guys are great!