When you open a csv file with Excel, and some of the numeric fields use 0 (zero) at the beginning of the serie, Excel will ignore them because of the automatic detection of the format, and these 0 will be removed form your numeric serie.
This can happen with EAN13 codes starting with 0, or with product references.
There is a solution explained in this video: https://www.youtube.com/watch?v=Gx5fwAt64NY
Please note that this is a issue related to MS Excel only, and the Store Commander team will not be able to provide more detailed information on this, nor assist you in applying the solution provided in this article.