Shipping incorrect on multiple quantities of the one product

-- url of the page with the problem -- : anniemauthor.com/
-- HikaShop version -- : starter 4.0.1
-- Joomla version -- : 3.9.2
-- PHP version -- : 7.1.26
-- Browser(s) name and version -- : Chrome 71.0.3578.98

Can you please help me find the reason why four of my orders have been overcharged shipping?
I have only the one product.
https://anniemauthor.com
I am using HikaShop Australia Post shipping plugin V2

Order number N2T93 Invoice number K2P20, sent to Queensland Australia, 10 books, $62.30 postage. Actually only cost $28.75 to post.

Order number L2A30 Invoice number H1C63, sent to Queensland Australia, 10 books, $62.30 postage. Actually only cost $28.75 to post.

Order number Q3N34 Invoice number M2A53, sent to Queensland Australia, ordered 4 books and was charged $52.20 in shipping. The parcel measured 38cm long x 28cm wide x 4.5cm deep, weighed 1.7kg and cost $16.25 to send.

Order number R3C47 Invoice Number M2M64, sent to South Australia, ordered 10 books and was charged $38.65 in shipping. It actually cost $21.60 to send.

Hello,

Your issue is probably coming from the fact that you have enabled the "Group products together" option of your AustraliaPost V2 shipping method, which is grouping products into the same package until the limit is reached.

You should test it with that option disabled.

Kind regards,
Mohamed Thelji.

Thankyou for your reply Mohamed.
If I disable the "Group products together" option, it charges multiple freights.

It turns out that my problem was an error in the dimensions of the product (this was only apparent with large multiple orders).
So now it is solved, thanks.