QUOTE(jasman0717 @ Oct 4 2007, 12:28 AM)

It is just an estimating tool so don't take it for exact science.

Also some consulates have more people filing, and doing timelines so that the database has more data to base an estimate than others.
China has hundreds of timelines, so is quite accurate, but others do not have as many timelines, or the timelines are incomplete, so a fair guesstimate is not possible.
Always remember: