What does compo marks meant in PSLE Chinese?

10/40 your compo is not completed and your language used are not up to par.

20/40 your compo is complete yet not interesting to read. Your language has a lot of problem like misspellings, grammar mistakes, wrong use of words etc.

30/40 your compo is good with good choice of words, proper use of complex sentences, and capability of advanced composition tactics. your story is complete and interesting to read.

40/40 your compo has excellence language use with good use of simile and other writing tactics. your story line is very interesting to read and has many twists and turns to the story.

If you want to improve your composition, you need to work on

1) vocabulary

2) sentence structure

3) good phrases

4) ways of expression like simile

5) good storyline

6) logical progression of events

7) pay attentions to detail

8) usage of advanced composition techniques like pre-frame etc

and more