How much yeast is in a "package"?
According to Red Star, a very common yeast brand in the US:
The strip contains three packets; each packet in the strip is considered one package. Each package contains 1/4 oz. or 2 1/4 teaspoons of yeast.
This is approximately 7 grams, or 11 ml.
This is representative of all of the US brands.
7g a sachet is standard in the UK, so it would seem to be somewhat standard
Measuring by volume is unusual for dry substances in the metric system. In most countries using metric, the sachet will be labelled by grams, not milliliters.