A distress signal, I hope?

For those who don't read Rey's journal... on the weekend, I went to my grandmother's 90th birthday party. Thanks to some nudging by my aunt, she got letters of congratulation from whoever-the-local-member-is, John Brumby, and the Rt. Honourable John Howard, Prime Minister of Australia.

...so, what does it mean when the signature on the PM's letter is upside-down?