This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. If an article link referred you here, you might want to go back and fix it to point directly to the intended page.
Chilia is the accusative neuter plural of "Chilio" which means thousand, put them together and you get 1000 years.
In verse 6 we have CHILIA ETH without the article referring to "a thousand years" indefinite, followed by verse 7 which has the article infront of it making it definite.
Also the adjective chilia can be neuter plural and would have ete ("years") as its implicit object.