The example from the course 
For example, let’s say you open a mini account which provides a 200:1 leverage or 0.5% margin. Mini accounts trade mini lots. Let’s say one mini lot equals $10,000.
If you were to open one mini-lot, instead of having to provide the full $10,000, you would only need $50 ($10,000 x 0.5% = $50).
Wouldn’t the margin be 0.0050 instead?
You need to spend a bit more time learning what is Lot (mini, micro, standard)), leverage, margin. Right now your question is not clear… F.e. having a mini-account it doesn’t mean you can trade only mini-Lot, also 1 mini-Lots means 10,000 Units not $10,000, 1 micro-Lot means 1,000 Units, 1 full standard Lot is 100,000 Units. Clarify, pls.
If leverage is 1:200 and you have $100 in your account it means you control (200 x 100) = $20,000 - sounds cool! Now if you wish to trade 1 mini-Lot in such an account you need to calculate “margin” - the amount in $ your broker will freeze while your position is open. Use this link Margin Calculator | Myfxbook where in Trading Size put 10,000 Units (1 mini-Lot). As you can see for the case of EUR/USD your margin will be $55.60. It means that you have only $44.40 ($100 - $55.60) for trading - this is called “free margin”. Now you need to know how much is the value of a pip for EUR/USD: Pips Calculator | Myfxbook You can see for your 1 mini-Lot it’s $1… It means if the EUR/USD market goes 45 pips against you - you’ll get a margin call as you’d be loosing $45: all of your “free margin” is taken by the pair move and you have reached your “margin” of $55.60. If you don’t add up to your account the broker will close your position and return “margin” of £55.60 (remember it was frozen earlier)… If, instead, you’ve opened a 1 micro-Lot position (1,000 Units) then to get to a margin call you need the market move of 450 pips against you… Hope it’s clear.