How To Correctly Calculates Time Achievement Performance

Question

Please kindly help. Our organization measure employee performance of time achievement with this formula:

Eficiency of time is calculated by:

• $[(TargetTime - TimeDone) / TargetTime] * 100%$

So,

1. If the eficiency of time is <=24%, then employee time performance is:

   $[ ((1,76 * TargetTime) - TimeDone) / TargetTime ] * 100%.$

   For future use, we will call this formula as F1

2. Whereas, if the eficiency of time is >24%, then employee performance of time is calculated by:

   $76 - (F1-100)$

I know there is assumption that the efficiency of 24% is excellent.

My question is: How can, say, if the time efficiency value is only different by 0,001% (23,999% and 24,001%) will make the employee performance score very contrast? Is it logically accepted?

Please somebody explain this to me. I very appreciate it.

Kindly Regards,

MAH