Hi Ravi,
When you are storing / removing a material in a Storage bin, system automatically assign a quant number to that. Quant is a combination of Plant, Material Number , Batch,Stock Category, Special stock and Quant identification.
if mixing is allowed in the Storage bin then you can store multiple quant in a bin
when you are looking LX03 quant field denote the material detail and the no of quant field denote no of SU / Quant stored in that Bin
Hope i understood your question correct and my reply is according to that.