private function calculateFirstItemOnPage()
    {
        // When an offset is used, increase the first item with 1
        $offsetItem = $this->getOffset() !== 0 ? 1 : 0;

        // When there are a total amount of items and the offset is zero, increase 1
        if ($this->getTotalItems() !== 0 && $offsetItem === 0) {
            $offsetItem = 1;
        }

        // Determine the first item on the page
        $firstItem = $this->getOffset() + $offsetItem;

        $this->setFirstItemOnPage((int)$firstItem);
    }