RDF 14.0.1 - Cumulative promo lift query

Hi,

I generated a forecast with 2 promo variables active in the forecast horizon for same item/store/week combination. In the forecast approval workbook, I inserted system calculated effect for both these variables.

Now, my understanding was approved forecast = (calculated effect var 1+ calculated effect var 2) * Baseline

However, there is a different between this value, which I calculated using above formula with the approved forecast generated by system.

Is there any coefficient RDF uses for each variable to assign weights? In some case forecast values differ by small units, but in some cases there is a big difference.

One example is attached in the mail. Is there any measure which can give me the cumulative lift effect of all variables active which can be seen in forecast approval view?