Cannot properly change shipping cost

-- url of the page with the problem -- : albertatacticalrifle.com
-- HikaShop version -- : 2.5.0
-- Joomla version -- : 3.4.3
-- PHP version -- : 5.6.10

I want to edit shipping price in an order from backend but I get problems.
Here is an order

Here is it in backend. I want to change shipping price i.e. to 30

And here is what I see, some strange numbers

How can I change shipping price to i.e. 30?

P.S.
I've managed to understand the logic. But it's not usable for usage then, if I have to manually calculate percents and substract them

How should it correctly work?

Hi,

This edition is indeed a manual edition, you have the possibility to set any amounts as you want.
The tax calculation is not made automatically in this part, we will see to add it on our todo list.

But do you often have to edit the shipping amount ? Just a question to have more informations to see how to manage this feature.

I've had to change shipping 3 times in the last two days...so

Here are my investigations, which have taken me many hours to understand how to make it work. I have to manually and carefully make 3 steps as per screenshot. This rather tiresome and generates errors as demands much attention. The example here uses round numbers, but in real life I need to calculate 5% from something like 16.25, so many numbers after comma.

Could you pleas fix it in the future?

I want some JS autocalculation to be added as I now I need to calculate two not obvious values instead of entering a value I want.

And the drop-down province list should be preselected correctly.

About the fact that you couldn't save the data with an uncompleted form, we will see to improve that too.

I don't understand what you mean. I could save all data.