Clarify what "deposit" does, explain the account model, explain when "cancel" is required

[protinam]

Explain what an Exchange account (proxy contract) is, and what a user is doing when they deposit assets. Clarify that assets can be withdrawn without cancelling orders.

User quotes:

Find using the site to be a bit confusing without some more explaination of how it works. When you go to buy something, there is no field for entering how many you'd like to buy. Then to sell I have to deposit first, yet there is no indication as to how many items I'll be depositing....

Say I have some galbi and I make a post on wyvern.... Where is my galbi? All of it just got sent to a contract? Why all of it? One of it? wat?

Which leaves me with zero trust of hitting submit
If I could specify the number of tokens, that would probably tell me that I'm not risking my entire balance to some contract
It seems like "Oh you put them all up and then the buyer comes along and then you decide how many you're going to sell to them".... but that's probably not right either

I created an order, then without knowing what it was trying to sell, panic closed it thinking I was potentially risking all my tokens of that type and potentialy selling them all for that price as a batch
I kinda assumed that perhaps it was a listing and then once a buyer came along there was another negotiation step where final approval and the number of tokens was decided