When you run a trading system on Collective2, you are allowed to open positions based on the nominal amount of capital you have in your C2 Model Account. Each financial instrument requires you to put up a different amount of collateral. To put this another way, each instrument can be traded with a different amount of leverage.
For forex, C2 allows only 33:1 leverage. (Or, in other words, you must hold as collateral 3% of the position amount in cash.)