PDF417 Macro File Id

[Colin Savage]

Hi

I'm hoping someone can help me with interpretation of the File Id part
of the macro control block in PDF417 barcodes. I don't have a copy of
the PDF417 spec, but I have one for MicroPDF417 which is supposed to
use the same macro construct (called "Structured Append").

From the spec:
"The two mandatory fields are encoded as follows: the segment index is
encoded in Numeric Compaction
mode and the file ID field is encoded as a sequence of base 900
numbers."

Does that mean the the file ID is always numeric? e.g. a file ID of
12345678 would be encoded as 015 217 378 ?

Thanks
Colin