77408 is the course_module id.
In Moodle, you have got
activities of all different types (quizzes, forums, pages, books, ...). They all have some settings in common, and those things are stored in the course_modules table. Then they have settings that are specific to the type of activity, and they are stored in tables like quiz, forum, page, ... (except for historical anomalies like that fact that name is stored in each separate table. Life would be easier (as a Moodle developer) if it was in course_modules, but it is too painful to change now, so we are stuck with it.
In course_modules, the 'module' column links to the 'modules' table, which tells you which type of activity it is, then the 'instance' column links to the id in the relevant table.
So, in your example, row 77408 of the course_modules table should contain 6603 in the instance column.