Overall average on summary report

I have built a report based on a table that compile the working time on different projects and another table with data specific to each project.

I need to find the Overall average time (MINUTES) worked per linear feet.

It goes well except for the average summary field that gives me a wrong number.

The project look like this:

Working time table project IDfk, dept, task, working time...

(This table contain thousands of data from hundreds of projects.)

Project table: project Id, linear feet (for each task)...

Both tables are related by the the project ID and project Idfk fields.

Report layer is based on the working time table.

Sub summary Project IDfk

Sub summary Dept,

Sub summary task , summary of working time(total_hrs), linear feet (from project table), cWorkingTime

cWorkingTime that look like this:

GetSummary ( total_hrs ; TaskIDfk) * 60) /

Case (

DeptIDfk = 1 ; PROD_Donnees_depart::depart_PL_Murs;

DeptIDfk = 2 ; PROD_Donnees_depart::depart_PL_Shapes;

DeptIDfk = 3 ; PROD_Donnees_depart::depart_PL_Murs_divisions;

"")

(8*60)/211 = 2.27

The case function goes to the project table to get the linear feet value from each task from different projects.

So far it goes well my results are good.

From there I just can't get the overall average time needed.

I have a table that look like this

On top summary of total time, my attempts of Averages

if you calculate the average per project and task : 2.27, 2.45, 1.11, 2.29 /4 = 2.03

So the overall average should be 2.03 but this is not what the average shows:

RESULT 2.27 is the cWorkingTime (the same as the field in the sub-summary part.)

RESULT 2.22 is a Summary field ith the average of cWorkingTime.

I have no idea why I can't get the right result.

I have tried so many different things to get that result right, I'M LOST.

Please help I really need that data ASAP

Thank you

Isabelle