value set max value?

 Hi,

I create a segment in Accounting flexfield,but when i am creating a value set and enter the max value 50 and save and apply on segment,it is not saving and error 25 is max value is allowed.Again i search that value set and change the max value from 50 to 25,it is not saving and error you cant decrease value.

I create another value set and enter the max value 25 and save.search same value set and change the max value from 25 to 50 and save.It save successfuly.

In both case from 25 to 50 and from 50 to 25.Why it is not accepting when i set 25 from 50?