What does 'Trade Size' mean?

Trade size refers to how much money you are going to be trading. It is usually represented by a number containing two decimal places up to the value of 1, and in integer form from then.

This value is proportional to a "lot" size, with a lot being 100,000 units of a currency.

So for example, if you work in dollars and place a trade of size 1 you are effectively trading $100,000!