I checked your file and everything seems to be correct. I think you need to learn how inventory costing works.
The reason why the amount credited to
Inventory on hand account is R253.22 upon sale is because that was the cost of inventory. No matter what you charge to customer, the cost of inventory won’t change. Cost of inventory amount is determined by how much inventory was purchased for.
To calculate cost of inventory, Manager is using weighed average method, see: http://guides.manager.io/businesses/inventory-items/costing-method
Amounts you have charged to customer are posted to
Inventory - sales income account.
I guess what’s confusing here is that you can click
View button in inventory on hand context which will give you the sales invoice. Instead of seeing an invoice which has different amounts, Manager should show some report to explain how did it calculate R253.22. So this is something I need to improve on.
Also, have a look at http://www.accountingcoach.com/inventory-and-cost-of-goods-sold/explanation which sheds more light on general principles used by Manager (or any accounting system with inventory for that matter)