Dear aspirants! I have not seen such rules in english grammar where shows a paragraph of 300 words. As a rule a paragraph carries only one idea and not multiple ideas. For the purpose you may consult Saddat English Grammar book in which paragraph rules have been clearly laid down.
Furthermore have you ever seen a paragraph containing 300 words.
Let suppose you people are examiners and there are two students/candidates who have attempted the same question. One candidate has focused only on production of mere empty words while the second one has stuffed his answer with relevant facts and figures let he has also crossed his words limits. Now let me know which answer you give more credit?
The answer is that who has struggled more God will help him and will get success.