Good Day, 

the reason you are getting 0 in that column is because they were added through a discovery scan or some other automated process. do a search in your assets tile, 

if you have none then all your assets will have a 0 in the CreatedByUserID, if it is manually created then this field is populated with something other than 0. 

so to recap this is expected if all your assets are added through an automated BeyondInsight process. you need to understand that that column is populated by the system. when you create an asset manually it will put a number in there that corresponds with your account in the Database. 

do a filter on your csv and in this column uncheck 0 and you will see assets created by others.

bottom line CreatedByUserID 0 is a system created asset.

I hope this helps

Frank Colvin