Making Dimensions Add Up
Let's start by removing some of the confusion by explaining that the rules are intended to address what the retailers are using the data for.
At the Consumer Item level dimensions are targeted to Shelf Space Management i.e. allowing the retailer to build a plan of how all the different products will fit on a shelf (this picture of the shelf is called a Plan-o-gram). The overriding consideration here is how the product sits on the shelf for the consumer to see. So there are a lot of rules that all boil down to two things: i) how to orient the product for the measurements and ii) how to obtain sufficiently accurate measurements so that the products will actually fit on the assigned shelf space. Again a lot of the detail in the rules is describing products where these answers are not obvious at first. A point to note on orientation is that it needs to match the orientation used for product images that you provide to the retailer for plan-o-gram purposes.
Moving on to other levels of packaging, the dimensions are focused on logistics purposes helping the retailer efficiently plan warehousing and onward transportation of the product. So the emphasis here is describing the orientation of the product as it normally rests. As with shelf planning the accuracy of the information is important retailers are striving to maximize full truck loads as they move product from Distribution Centers to Stores.
At both levels, accuracy is important. Retailers are counting on more accurate data to optimize that last bit of shelf space and last bit of truck and warehouse space and they are counting on Data Sync providing them the data sooner so they can plan ahead.
Finally certain retailers are asking for out-of-box dimensions. These would be the dimensions of the product out of its packaging and are typically of interest to consumers perhaps to determine if the item will fit in a space in their home. Accuracy here is important to avoid the consumer returning the item and being unhappy with the brand.
For more information the packaging measurement rules are available at www.gs1.org/docs/gsmp/gdsn/GDSN_Package_Measurement_Rules.pdf