Calculation of margin for spot Forex?

How is the margin calculated for spot forex pairs ?

For example, I was looking at a system that entered long EUR/USD pair 40 contracts at 1.2743.

It showed the margin as 15,300$ (approximately).

However, if I were to trade spot forex, based upon my leverage my margin requirement could be between $1,000 (400:1 leverage) to $8,000(50:1 leverage).

Where can I did details on how margin is calculated by C2 ?

C2 “gives” 33:1 leverage. This is typically lower than many forex dealers, but the reason for this is to allow some kind of meaningful comparison between forex, futures, and stock trading systems on C2. Of course, in real life, you (or your autotraders) could choose to employ more margin when trading your strategy. There’s no reason you need to use only 33:1 margin in real life trading.