Revaluation Value issue...

SUGGESTED

I am trying to make revaluation but,am getting this attached error.atleast i want to know how do i revalue.assets thats there value has reduced

for example i have an asset that has 28m book value and it has depreciated to 12m.when i put the reduced value i get the error attached 

i have also tried impairement and recieved the error that the impairment value is less than book value.

in sage evolution how do i capture revaluation value in sage 200 kindly help.

i will be glad.

Alex