That student would receive a score of 15 points out of a possible 20 points. Does 75% (15 out of 20) capture that performance for you? Perhaps you think a student should not receive that high of a score with only "sometimes" for the summary. You can adjust for that by increasing the weight you assign that criterion. Or, imagine a student apparently put a lot of work into the homework problems but got few of them correct. Do you think that student should receive some credit? Then you would need to adjust the holistic homework problem rubric above. In other words, it can be very helpful to play out a variety of performance combinations before you actually administer the rubric. It helps you see the forest through the trees.
The essay shows little or no understanding of the task. If the essay takes a position, it fails to convey reasons to support that position. The essay is minimally developed. The essay may include excessive repetition of the writer's ideas or of ideas in the prompt. Focus on the general topic is usually maintained, but focus on the specific issue in the prompt may not be maintained. There is little or no evidence of an organizational structure or of the logical grouping of ideas. Transitions are rarely used. If present, an introduction and conclusion are minimal. Sentence structure and word choice are simple. Errors may be frequently distracting and may significantly impede understanding.