Semester 1 and Semester 2 grades are totally different things. If you are in High school, or are in advanced track middle school class, than Semester 1 and 2 grades go onto your high school transcript that colleges see.Overall grade just refers to how you are doing in a class at a certain point of time.
Let's look at Edge for a second. Overall grade is "the grade on the work you have submitted. No penalty for any missing or overdue assignments".
Think of this in the way you would for colleges or uni; Semester one is your "first final", Semester two is the "second final". Grades to not carry over from Semester 1 to two. They are completely and utterly unrelated.
I hope this helped, although my explanation may be a little confusing. I hope you understand better.
a free ticket. 2a : having the legal and political rights of a citizen For many African Americans, celebrating the Fourth of July as the day Americans became free from British rule feels inapplicable since our ancestors were not free.—