How system calculate quantity in part list based on BOM

Hi,

I have an item A001 whose primary UOM is EA whereas for same item BOM is defined with Batch quantity as blank, next to this UOM field is there and in this it's defined as CA. Under this multiple items are defined and are having UM as KG, LT, MT, GM with some quantity. I have created WO for A001 in 500 EA and attached the part list. When checking I found that system has fetched items with some different quantity. I am not able to figure out how system has calculated quantity in part list. Can anyone help me