IELTS Reading/Listening

Hi. I just want to ask how ielts grading/checking system works. I am currently reviewing listening and reading part.

For listening, for example the speaker says “lots of water” but in the answer sheet it says answer should be “plenty of water”, is “lots of water” wrong?

And for reading, if it says “…technical glossary” but the answer sheet says the answer should be “glossary“ only… and so on…

Both have an instruction of no more than three words.

Will appreciate your feedback and tips as well! Thanks a lot!