I hope I'm not the only one confused by what that said.

If you're asking what I think you're asking then you missed one important thing. Your maximum storage capacity of your warehouse remains just that, your maximum storage capacity.

If you move goods from your warehouse to your trading post for sale then the storage space is temporarily alloted to the trading post instead of your warehouse. That means if you could hold 1000 goods in your warehouse and move 500 to your trading post, your maximum storage limit will drop by 500 as well. You are still storing the goods, its just that you can no longer withdraw them from your warehouse for use until you remove them from the trading post.

If you had a maximum capacity of 500 and moved 2 units to your trading post then your maximum capacity would drop to 498. If you moved them back out to your warehouse it would go back up to 500.

BTW, if you're selling luxury goods (marble, sulfur, crystal, and wine) for less than 8 gold then you might as well give it away because you're taking a loss. It takes 2 citizens to harvest one luxury resource and each citizen naturally produces 4 gold per hour in taxes. That means, at the minimum, it costs you 8 gold for the 2 citizens it takes to collect 1 luxury resource per hour. On that note it takes 4 gold or 1 citizen per hour to collect 1 unit of wood.

Prices may vary from location to location, but if you're planning on selling your resources for below cost then you're better off pulling your workers out of the node and leaving them as citizens to tax.