It is a metaphor that is used to refers to a phase of development in which start-ups are not ready yet to "deliver" (the service or product) they were set up for but they should continue in their business.
You could say that the are midway in the development of their product or service.
It's short for "you got it right after only one guess."
It's the equivalent of the phrase "a hole in one" in golf, meaning that you managed to get the ball into the hole after only one shot.
Fred could also have said:
"You guessed it."
"That's what happened."
In other words, Hermione was "right" in that she was indignant about the possibility that Bagman would have refused to give the money back.
This bit is tricky because the conversation reverses the literal meaning of her words.
Her response could also have been phrased as:
"Surely he didn't refuse!"
"Don't tell me he refused!"
The extended dialogue could have gone like this:
“So we asked for our money back,” said George glowering.
“Don't tell me he refused!” gasped Hermione.
"You guessed it,” said Fred.
Best Answer
Here 'right on the line' means 'at a threshhold' of some kind. The exact meaning depends on the context of the article, but the phrase implies the 'others' could go one way or the other.