Well - in the table you have a screenshot of this expression should do the sum you're asking for:
Add an extra column and use the above expression just to verify that it calculates to 36 on all the rows.
If it does not return 36 on all rows it might be a "Sum of Expression" that does not calculate to the same of "Sum of Rows". Then the solution is often using the fantastic advanced aggregation function Aggr(...):
Sum( Aggr( Sum([DagMatriseVerdi2018%]) , %ProposalLine_%UkeID_Key ) )