Ann: Appendix 4D and Half Year Financial Report, page-14

I think it's most likely a combination of tactical responses:

1) Some holders who were well in profit after the last two weeks of trading would be encouraged to lock in their profits in the face of US market weakness. A sensible move.

2) Some traders could be trying to trigger a sell-down by "selling on the news" hoping this will combine with negative sentiment about the US market drop to spook holders into off-loading.

3) It wasn't the hoped-for big news, even though the report itself was solidly in line with expectations.