Hi the value has been increment everytime when i refresh the page

Hi there, I worked on check out page and got the data using a session like this. I pass the data perfectly and retrieve it without errors, but when I refresh the page, the data is incremented. Here is my code (Controller).

        if(session()->has('user_name') || session()->has('user_id') ){
$user_name = session('user_name');
            $people = session('people');
            $total = session('total');
            $slot_price= session('slot_price');
            $slot_time= session('slot_time');
            $date= session('date');
            $month= session('month');
            $additional_product = session('additional_product');
            $baseAmount = $people * $slot_price; 
            $gstamount = (5 / 100) * $total ; //1600
            $baseAmount = $baseAmount - $gstamount;
            session()->put('gst', $gstamount);
                $addpprice = '0';
                foreach($additional_product as $product) {
                    $addpprice = $addpprice + $product['price'];
                    session()->put('total',$total + $addpprice);
                }
}

Any suggestion or solution ?