How to loop input field value and insert to its row based on the database value in Laravel?

My problem is that I want to update the quantity_served based on quantity and insert the last loop value into the last record based on the input value.

For example, my input value has 180.

My code doesn't insert the last value of loop instead of the full value of quantity.

$var = $request->get('id');
$data = bulkcorporatemodel::orderBy('id', 'asc');

foreach ($data as $item)
{
    if ($var == 0 || $var < 0)
    {
        break;
    }

    $bulkcorp = bulkcorporatemodel::find($item->id);
    $dummyHolder = $bulkcorp->quantity;
    $bulkcorp->quantity_served = $dummyHolder;
    $bulkcorp->save();

    $success_output = '<div class="alert alert-success">BULK DATA UPDATED</div>';
    $var = $var - $dummyHolder;
} 

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