Barcodes / Label printing question

Does the function "Serialization" in RMS, affect or perform any validation of the Item Lookup Code length, and that Items corresponding or selected barcode?
We use 128-A, and use Retail Realms Fashion Bundle to create UPC numbers. In RMS Serialization is Off. RMS manual states barcodes must be 12 digits and no letters, however, it allows more digits, and letters, to be used as an Item Lookup, and doesnt display any error when selecting barcode 128-A and printing.
It seems it will print anything, but the actual printed barcode may not really be the complete Item Lookup code, if this number is over 12 digits?
Does any validation get done prior to printing in RMS, or is it a shot in the dark until I find a combination of settings that produces a consistent barcode?
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