When is 99.99% actually 99.996% ?

When it's a Perth Mint standard.

GOLD PURITY - Perth Mint - Allegations of 'doping'

The Perth Mint has responded to an ABC Four Corners program on 6 March 2023 which alleged that The Perth Mint could face a potential recall of $9 billion worth of ‘doped’ one-kilogram gold bars from customers in China.

Here's the Perth Mint's response to those allegations.