An additional 7 were in the can by the time the series premiered on September 28th.
Which would give them nine completed episodes when you factor in Farpoint
, plus "in the can" means completely done and ready for airing. I'm sure they probably had some that were shot and still waiting for post-production processing.
The ratings did continue to get better the longer the show ran, but it was an unqualified hit right out of the gate and never lost steam from a ratings perspective.