From your perspective as a student, a Numerical question looks just like a regular short-answer box. However, it is specifically designed to handle math and science answers more fairly than a text box would. 

• Check the instructions: Read if the question asks for a specific number of decimal places.
• Don't use text: Only enter numbers and, if required, the unit. Do not type words like "about" or "roughly" unless specifically told to do so.
• Units matter: Always look for a unit box or a mention of units in the question text to avoid losing easy points.