The scanner does not allow for you to change on the Put-Away as it is controlled by the Document you have setup in your Business central.
On the scanner the Lot number options typically is grayed out by default, therefore not allowing you to changing it at all.
Per base Business central process, you receive your item via the receipt, once the receipt is registered you create the put-away and there you log in the Lot No. you use. Once you proceed with your Put-away this cannot change your Lot No. as you have a corresponding document that will not allow for the change. Even on the Put-away screen in Business Central you will not be able to modify the Lot No.