Instance names should "AF1", "AF2", "AF3", etc.
The "Device" parameter is the same for all instances.
The "Name" parameter should be "Aeration Fan 1", "Aeration Fan 2", etc.
Not that it helps in the short term, but for posterity @Gerardo_Bolanos completely revamped the multi-instance wizard in 8.3, and now it's easily capable of this task (and a lot more):
The multi-instance wizard is the piece of GUI that lives in the designer whose sole purpose is "make a bunch of UDT instances following some standardized pattern".
You are capable of making tags, including UDT instances, via the REST API in 8.3, but that's orthogonal to the wizard GUI.