Upvote:4
I flew out of Beijing in November. The departure boards and my boarding pass both told me a gate with a letter and a number. I believe mine was E7. The signs then said both International/Domestic (more complicated than that because Macao, Hong Kong, and Taiwan are not international in China's opinion, so it's "International plus Macao, Hong Kong, and Taiwan" / "Domestic") as well as indicating the letters, eg "E Gates."
As a result you're unlikely to get it wrong. That said, it seems likely that your first leg will be domestic, and you'll do an international departure (including passport checks) in Xiamen.