This was the code I am trying. Last Updated is the name of the extension field in the UI which I declared in the BO. But it shows an error saying Lastupdated can be identified.
import
ABSL
;
if
(this.CurrentCommon.LastUpdated.IsInitial
()) {
this
.LastUpdated.content = this.LastActivityDate.Delta(Context.GetCurrentUserDate()).ConvertToDays
();
this
.LastUpdated.unitCode = "DAY"
;