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();

dd($data)                

and this the result

   2491 => {#2822 …26}
    2492 => {#2823 …26}
    2493 => {#2824 …26}
    2494 => {#2825 …26}
    2495 => {#2826 …26}
    2496 => {#2827 …26}
    2497 => {#2828 …26}
    2498 => {#2829 …26}
    2499 => {#2830 …26}

via Chebli Mohamed