I hope this message finds you well and congratulations on undertaking this particular legal writing task. What is generally meant by keeping it brief is to not be duplicative or to have any unnecessary information in your legal document. In other words, there is a premium on efficient writing.
You want the reader to be well aware of what the claims are, their nexus and their basis in the law. You want to keep your sentences fairly short and concise. You want them to read well and you need to scan the document to extract anything that does not move your argument forward.
The examples that you have added are perfectly fine and will be needed. Leave them in there but make sure that only the information necessary to move the narrative forward is present.
Keep your paragraphs as short as possible...no one wants to see a piece of paper and see what amounts to a wall of prose. Two and three sentence paragraphs are welcome for a reader.
In short, legal writing is less about length and more about efficiency. Remove the fat and leave the muscle and bone. If you want to look at good legal writing examples, I suggest you find a couple of opinions written by Judge XXXXX XXXXX that used to sit on the United States Fifth Circuit Court of Appeals. He was a brilliant legal writer. When you read one of his opinions, you will see a master at work...someone to emulate in style and prose.
Let me know if you have any additional questions or comments.
Best wishes going forward!