RPN Value in FMEA

Hi,

In FMEA the Risk Priority Number(RPN) is calculated by using folowing formula

RPN = Severity of the Effect X Probability of Occurence of the cause X Probability of the Detection

490 = 7 X 7 X 10

Now the problem is Probability of detection value is taking default as 10 even thought the valuation proposal is 8.where as Effect(7) and cause(7)values are taking from valuation which are correct .

Please anyone can guide me how to prevent default value considaration of detection.

Regards,

Raj