eCommerce with Gtag

Hi - I'm looking at this guide for Google eCommerce integration.

https://developers.google.com/analytics/devguides/collection/gtagjs/ecommerce

On their site, this is how it says it needs to be set up.

Code:

gtag('event', 'purchase', {
  "transaction_id": "24.031608523954162",
  "affiliation": "Google online store",
  "value": 23.07,
  "currency": "USD",
  "tax": 1.24,
  "shipping": 0,
  "items": [
    {
      "id": "P12345",
      "name": "Android Warhol T-Shirt",
      "list_name": "Search Results",
      "brand": "Google",
      "category": "Apparel/T-Shirts",
      "variant": "Black",
      "list_position": 1,
      "quantity": 2,
      "price": '2.0'
    },
    {
      "id": "P67890",
      "name": "Flame challenge TShirt",
      "list_name": "Search Results",
      "brand": "MyBrand",
      "category": "Apparel/T-Shirts",
      "variant": "Red",
      "list_position": 2,
      "quantity": 1,
      "price": '3.0'
    }
  ]
});

On aMember side it says this:

The following variables will be automatically replaced:
%payment.tax%
%payment.amount%
%payment.dattm%
%payment.discount%
%invoice.public_id%
%user.email%
%afflogin%
%affkeyword%
you may also use %foreach_product% and %endforeach_product% tags
to run cycle for all items in invoice, you may use %item.item_title% %item.qty% %item.first_total% %item.item_id% and similar variables inside

Which is cool. I'm a little concerned about the comma "," though

[{item1},{item2}, {item3}] is the syntax google wants.

Here's what I think it is looking for:

Code:

gtag('event', 'purchase', {
  "transaction_id": "%invoice.public_id%",
  "affiliation": "aMember",
  "value": %payment.amount%,
  "currency": "USD",
  "tax": 0
  "shipping": 0,
  "items": [
%foreach_product%
    {
      "id": "%item.item_id%",
      "name": "%item.item_title%",
      "list_name": "Search Results",
      "brand": "Jigsaw",
      "category": "Jigsaw",
      "variant": "",
      "list_position": 1,
      "quantity": %item.qty%,
      "price": '%item.first_total%'
    }
%endforeach_product%
  ]
});

A couple of things I don't get.
- Will it replace the item between the %%, even if there is "" around it?
- What does it do about the comma "," between the products? Does it put it in?
- Has anyone else done this with Google eCommerce tracking? I'd love to see an example.

Best regards

Peter