WebCourses grade book imports the scores in WebAssign while you are doing your assignments or taking an exam.

When you submit each problem, your score will be updated. I don't know whether the WebCourses grade book updates the scores every time you submit each question's answer. But if you work on the problems and take a break for a while, then WebCourses grade book will update your score so that what appears on the grade book becomes the most recent score you achieved. If you make progress again, then the grade book will update the score again.

You don't have to submit the entire assignment or exam by clicking the 'submit' button on the bottom of the assignments/exam page.

Since WebCourses grade book continues to update your scores, you don't have to be worried about the score which emerges on the WebCourses grade book by thinking that the score which appears on the WebCourses grade book is the final score.