Guild Wars 2

I there.

I have some doubts about the trading post fees when selling stuff.
In the wiki link: https://wiki.guildwars2.com/wiki/Trading_Post
it says:
Additional fees
Selling items on the Trading Post requires additional coin fees, based on the total sale price.
Listing Fee (5%) — This nonrefundable cost covers listing and holding your items for sale. This fee has a minimum of 1 Copper coin.
Exchange Fee (10%) — After a successful trade, the item exchange fee is deducted from coins delivered to the seller. This fee has a minimum of 1 Copper coin.

I don’t get how this fees work even after doing some math with real examples, the numbers just aren’t right, so i guess i’m doing something wrong.

1.
Let’s say i want to place a item for sale costing 3g 25s 00b
The listing fee is: 16s 25b
The exchange fee is: 32s 50b
When i sell it what is the actually money that i get from the 3g 25s 00b?

Or, for the same item

2.
Let’s say i want to sell it instantly for 3g 13s 18b
The listing fee is: 15s 66b
The exchange fee is: 31s 32b
Again, when i sell it what is the actually money i get from the 3g 13s 18b?

If possible could someone help me to decipher the maths behind this two examples?

Thanks in advantage,
Kensishi