protected function generateAverage($staff, $type)
{
    $months = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
    $staff = array_map(function ($row) use ($type) {
        if ($row['row_type'] == $type) {
            return $row;
        }
    }, $staff);

    foreach ($staff as $key => $employee) {
        $months[0] += $employee['amounts'][0];
        $months[1] += $employee['amounts'][1];
        $months[2] += $employee['amounts'][2];
        $months[3] += $employee['amounts'][3];
        $months[4] += $employee['amounts'][4];
        $months[5] += $employee['amounts'][5];
        $months[6] += $employee['amounts'][6];
        $months[7] += $employee['amounts'][7];
        $months[8] += $employee['amounts'][8];
        $months[9] += $employee['amounts'][9];
        $months[10] += $employee['amounts'][10];
        $months[11] += $employee['amounts'][11];
    }
    $months = array_map(function ($value) use ($staff) {
        return $value / (count($staff) / 2);
    }, $months);
    $months[] = array_sum($months);
    return $months;
}

array:6 [
  0 => array:4 [
    "amounts" => array:13 [
      0 => "30000.00"
      1 => "30000.00"
      2 => "30000.00"
      3 => "30000.00"
      4 => "30000.00"
      5 => "30000.00"
      6 => "30000.00"
      7 => "30000.00"
      8 => "30000.00"
      9 => "30000.00"
      10 => "30000.00"
      11 => "30000.00"
      12 => 360000.0
    ]
    "image" => "test.jpg"
    "row_name" => "Target"
    "row_type" => "target"
  ]
...

$data['aggregates']['Target average'] = $this->generateAverage(array_values($data['staff']), 'target');