How to convert item to negative value

[nsh15]

I am trying to make calculated item that changes the sign of another key.
Whenever I try to multiply with negative values, the item goes grey and stop working.

Please, let me know the correct way to reverse the sign for calculate item to be negative.

Thanks

[Semiadmin]

Just change Type of information to Numeric (float)

[nsh15]

Thank you for your answer.
I changed the type to float for the new calculated item and it totally disappeared from latest data page.
when the type is unsigned it appears grey