An inventory number identifier may be associated with an item number of an inventory account within a system inventory. The inventory number identifier may indicate a number of units of the item available for purchase according to the inventory account of a user. The inventory number identifier may be selected for inclusion among one or more selected identifiers for advertisement generation. An advertisement including the selected identifiers for the item may be generated. The advertisement may be made available within a first system for an item in an inventory account of a user of a second system. The inventory number identifier of the advertisement may be updated by accessing the inventory account of the user. The advertisement may then be displayed within the first system.