What it teaches
Getting information out of a sentence, which is the point of reading and is almost never practised at this length. A child can read every word of a sentence aloud and not be able to say who did what.
One sentence is deliberate. A paragraph brings memory into it, and memory is not what is being tested.
What to look for
This is the best single predictor on the site of how a child will get on with written work at school. A child who is fast at the other reading games and slow here is decoding well and comprehending less, which is common and worth knowing.