I think you just solved this. DPCK is likely "Derivative Pack" which breaks down the standard items for the particular model trim. My S has a DPCK of ZL14, which includes a list of items... trim level 4, bumpers plastic sport, badge S AWD, garage door opener...... and so on. In other words, when you order a trim level, it is assigned a derivative pack (DPCK) specific to that trim level. Note that the above list shows all of the options and then the base trim level pack. It all makes sense to me now...