How does the system make up the default example sentence?

I notice in most cases, the system starts from 5 words before the new word and cuts off after the 5th words after the new word.

But sometimes it is doing something different. What is the rule?

It’s 5 before and 5 after, as you noted. The difference that you’re noticing may be due to the fact that it stops when there’s a paragraph break.

So if I edit the text such that each sentence is followed by a linebreak (
), each time when I create a LingQ, the system should be able to cut out the sentence properly?

Sorry, then it will still cut off at the 5-word marks. Never mind.