There are few different types of labels that Amazon provides for sellers. Please see information about each below:
Amazon Customer Orders - These are orders to fulfill customer orders. You may simply leave the layout as "default" and this will produce a label in 4x6 size in the proper format for AIMO and other thermal printers.
Amazon ASIN product labels - These are the labels to place on products before sending to Amazon. You may also send these directly to AIMO from Amazon's Scan & ship page:Printing FBA Product ASIN labels.
Amazon FBA Labels for outside the box - These are the labels that are placed outside of the box containing your product that is being sent to Amazon's warehouse.
The AIMO team has put together a free service that can crop multiple pages into a 4x6 format.