When you choose your own packaging size it does not matter what price click and send gives you.

My registered click and send is in a country zone but i post from a city zone and when i print off the labels for my own packed items it always comes up with a price for my address, in the country zone

but

as you do not pay until you get to the post office it does not matter. The post office you go to will always weigh and/or measure and give you the correct price

If you are ony printing off labels to pack items to take to the post office and not paying online, dont stress.