Negative Values allowed at asset class level

Hi Gurus,

We want to activate the check box available for the field "Negative Values Allowed" in Dep.area-32 for asset class-XXXX in OAYZ transaction code but its grayed-out and not able to activate it. I have checked screen layout as well. Same screen layout(1000) used for different chart of depreciations & its allowing me to update this checkbox under different chart of depreciation.  Where would be the control for making changes here in OAYZ.

Thanks in advance.