Formula for number of perfect ordered needed to achieve certain target.

Hi all,

I was working on a chart to calculate my Amazon seller rating to see how many more perfect order I need to hit my next target grade. Here is how the calculation works.

Order with no problem gets 100 points per order
Minor problem gets 0 point
Moderate problem minus 100 points
Severe problem minus 500 points

Grade are evaluate by:
<84.5 Fair
<96.5 Good
<98.5 Very good
Above is Excellent

Total points / total orders = final grade (or percentage)
As of now i got
53800 (points) / 624 (orders) = 86.22(%)
Now that I know what grade I've got so far and I also want to know how many more perfect orders I need to achieve my next targets or in case some bad orders come by and how far they pull me down.

Attached is my work sheet so far and I'm just missing the calculation for the orange shaded part.

Please help.

Thank you!!!