The weighted system calculates grade items as a percentage of a final grade worth 100%. The Max. Points you assign to individual grade items can be any value, but their contribution towards the category they belong to and the final grade is the percentage value (weight) assigned to them.
Grade items in a category count as a percentage of that category, not of the final grade. Therefore, grade items in a category should combine to a weight of 100%.
For example, if you have a category worth 10% of the final grade with two equally weighted grade items, the weight of each grade item is 50%, (its contribution to the category), not 5% (its contribution to the final grade).
Since it's a category’s weight and not an individual grade item’s weight that counts toward the final grade, the final grade is inaccurate until all the items in the category are graded. Therefore, releasing calculated final grades to users before the end of the course might be misleading.
If your grade items do not add up to 100% you receive a warning message. You can ignore this message if you choose; a balanced grade book is not required. If the weights assigned to grade items do not sum to 100%, the tool adjusts the weight of each item. For example if you have three grade items with a weight of 25% each, each item is actually calculated as 33%. This is true for categories and the final grade.