Either the ABNF grammar for the ATRN command is broken (most likely) or the examples are broken.
The ABNF allows no spaces (at all) in the ATRN command. That is
ATRNmunnari.oz.au
is valid, but
ATRN munnari.oz.au
is not. The examples show spaces both after the "ATRN" and after the comma that separates domains.
kre