Why does cart_token change inconsistently when adding products?

Hi Shopify support team,

I am doing with add_to_cart and checkout with my store, the issue that I am facing is:

when I add product 1st and then call API/cart.js, it returns token ‘xxxxxxxx’

when I add product 2nd and then call API/cart.js, it returns token ‘xxxxxxxxx’

when I add product 3rd and then call API/cart.js, it returns token ‘yyyyyyyy’

when I add product 4th and then call API/cart.js, it returns token ‘yyyyyyyy’

when I add product 5th and then call API/cart.js, it returns token ‘yyyyyyyy’

when I add product 6th and then call API/cart.js, it return token ‘zzzzzzzzz’

and then I check out, Shopify pushes an order hook with data

‘zzzzzzzzz’ - [{product1, price1},{product2, price2},{product3, price3},…]

So, I wanted to know when the cart_token change, with the above example, sometimes it still keep the old value when adding a new product (product 1st → 2nd, product 3rd → 5th,..), and sometimes it changes (product 2nd → 3rd)

I saw a thread (https://community.shopify.com/c/shopify-apis-and-sdks/cart-token-specification/td-p/588359)

that it tells the cart token will change every add a new product, compare with my case, it is not consistent