The Batch String is a free text field that can be set by the user to provide some contextual meaning to the device. Usually it is shipped with the shipment date (eg "Shipment 2016/10/18"). It can be changed to anything required by the vendor, so as "Not installed", "Input 1 not connected", etc.
To set the Batch String:
Select an asset or assets:
Go to Device Operations (1); Set Batch String (2)
Type in the batch string(1) you would like to use.
Then click on the OK button (2)