Reader---I'll show an example of margin usage here. It will be generic, but you'll get the idea. For this example, we'll use an ES contract size of $100,000. (it's a little more than that currently). We'll also assume a trading account size of $100,000
-----So, for a trade with 10 X margin, you would need to trade enough contracts to control $1,000,000 worth of ES. That would be 10 contracts (10 time 100k equals 1 mil).
----A trade with 4 X margin, you would need to trade enough contracts to control $400,000 worth of ES. That would be 4 contracts (4 times 100k equals 400k)