Why when I use Query Builder the data level becomes a lot

I use Query builder in laravel in the first table (student) there are 500 data in my second table (class) there are 35 classes, why the data becomes more than 2000 , even though I only want to bring up 35 data in suitable with the (class) table.

Here is my code:

 $data = DB::table('class')
                ->join('student', 'class.student_id', '=', 'student.id')
                ->select('class.*','student.*')
                ->get();

via Chebli Mohamed