Opmanager monitor "Units" is in percentage even after changing to "GB"

Opmanager monitor "Units" is in percentage even after changing to "GB"

I want to monitor my disk space in GB instead of percentage % because different disk has different sizes and percentage is not the best way to monitor disk space for 100s of servers.

I tried to change monitor units to GB but it still gives me % value, see screenshot attached.

any help to rectify this issue.

Thanks