I have calculated two KPIs. Both work and give me a result per each case. Both calculations use the source / target function and they calculate for different status the total time. When I try to substract or add the KPIs i get the following error message. I can't even use them in a chart when using the average of both. Why?

ERROR MESSAGE:

No common table could be found. The tables <Temporary table: SOURCE/TARGET configuration _CEL_SF_ACTIVITIES,REMAP_VALUES ( "_CEL_SF_ACTIVITIES"."ACTIVITY_EN" , 'Set Status to Information Received - Email' , 'Set Status to Information Received - Email' ] , 'Set Status to Awaiting Customer Information' , 'Set Status to Awaiting Customer Information' ] , NULL ),ANY_OCCURRENCE ] TO ANY_OCCURRENCE ]>] and <Temporary table: SOURCE/TARGET configuration _CEL_SF_ACTIVITIES,REMAP_VALUES ( "_CEL_SF_ACTIVITIES"."ACTIVITY_EN" , 'Set Status to In Progress' , 'Set Status to In Progress' ] , 'Set Status to Resolved' , 'Set Status to Resolved' ] , NULL ),ANY_OCCURRENCE ] TO ANY_OCCURRENCE ]>] are connected, but have no common table. This means that they do not have a direct (or indirect) 1:N or N:1 relationship. Join path: Temporary table: SOURCE/TARGET configuration _CEL_SF_ACTIVITIES,REMAP_VALUES ( "_CEL_SF_ACTIVITIES"."ACTIVITY_EN" , 'Set Status to Information Received - Email' , 'Set Status to Information Received - Email' ] , 'Set Status to Awaiting Customer Information' , 'Set Status to Awaiting Customer Information' ] , NULL ),ANY_OCCURRENCE ] TO ANY_OCCURRENCE ]]N <-- 1!!_CEL_SF_Case]!1 --> NNTemporary table: SOURCE/TARGET configuration _CEL_SF_ACTIVITIES,REMAP_VALUES ( "_CEL_SF_ACTIVITIES"."ACTIVITY_EN" , 'Set Status to In Progress' , 'Set Status to In Progress' ] , 'Set Status to Resolved' , 'Set Status to Resolved' ] , NULL ),ANY_OCCURRENCE ] TO ANY_OCCURRENCE ]]. For more information on the join path, search for "Join functionality" in PQL documentation.