How to change total according to item quantity - node.js

Question

I've got a paypal payment at my site. Looks like this:
app.post('/pay', (req, res) => {
console.log(req.body);
const create_payment_json = {
"intent": "sale",
"payer": {
"payment_method": "paypal"
},
"redirect_urls": {
"return_url": "http://localhost:1234/success",
"cancel_url": "http://localhost:1234/cancel"
},
"transactions": [{
"item_list": {
"items": [{
"name": req.body.user_name,
"sku": "001",
"price": "25",
"currency": "USD",
"quantity": req.body.persons_count
}]
},
"amount": {
"currency": "USD",
"total": "25"
},
"description": req.body.user_name + " with email " + req.body.email + " just ordered " + req.body.persons_count + " places"
}]
};
paypal.payment.create(create_payment_json, function (error, payment) {
if (error) {
throw error;
} else {
res.send('on my way');
console.log(payment);
}
});
})
If I change total field in amount object (this is what I wanna do) I get a 400 response (bad request). How can I make a payment like this:
"amount":{
"total": req.body.persons_count * 2
}
Where req.body.persons_count variable is a variable I get from a post request from one of the forms I have earlier.
Fighting with that code showed, that both price and total values have to be equal however I want the price of a single item be different from the total amount I wanna get. Huge thanks!
By the way quantity value has to be equal to 1. In all other cases app crahes.

Answer 1

Total amount should be sum of items amount, shipping amount, tax and other fees.
In your case, total : Item price * Item quantity
sample,
"transactions": [
{
"amount": {
"currency": "USD",
"total": "20",
"details": {
"shipping": "1.20",
"tax": "1.30",
"subtotal": "17.50"
}
},
"description": "Payment description",
"invoice_number": "1231123524",
"custom": "custom data",
"item_list": {
"items": [
{
"name": "Ground Coffee 40 oz",
"currency": "USD",
"quantity": 1,
"price": "7.50"
},
{
"name": "Granola bars",
"currency": "USD",
"quantity": 5,
"price": "2"
}
]
}
}
]
You can also refer https://developer.paypal.com/docs/api/payments/v1/#payment_create