data migration project forecast

Summary: Client has project forecast information in a number of external applications. We need to upload those forecasts into Project Portfolio Management. For some projects the forecast information is period based while for large projects the forecast is Whole Of Life, i.e. for the remainder of the project duration. We loaded a period based forecast, but the amounts show in the application don't add up at all. Has any one uploaded forecast information either period based, or project remainder of life or both successfully? If yes what are the (configuration) items to be aware of.

Appreciate your help

Chris