Without a little more information it will be hard to answer this...
But first off, Data Warehouse is sort of a flattened table of data... When you have fields (such as lists or products) that contain multiple pieces of info, that "one" row will actually present as many.
Example, an order with 3 products will actually present as three rows in the export (one for each product)... this also means if you are adding up your metrics, you will actually over count them...
This one "Order" will show the order metric in each row, if it's tracked on a page view, it will also track the same page view in each row... so "1" becomes "3" because it cannot be de-duplicated.
Even when not looking at list type items, metrics like Visits or Unique Visitors can be inflated, again due to the inability to de-duplicate across your rows...
The better solution is to use the Raw Data Feeds... this will actually provide you with the Raw Data as Adobe gets it... but it's also not for the faint of heart... because now you will have to create all the SQL to process the information like Adobe: identifying your UVs and Visits, excluding the hits that shouldn't be counted, processing all the information... and while you may not get a 100% match (since it is challenging to replicate all the logic), you should be able to get it very very close...