Increase in Margin Requirements - Please help

making the correct topic location for another users post.

How can I calculate this?

According to this article:

  1. Calculate the value of the trade:
    574.31 at current price right? so that’s £430 x 50 quantity that I have = £21,500 and that is the value of the trade.

  2. See how much funds you need to have to cover 50% of the value of the trade:
    Value of the trade = £21,500 x 0.5 = £10.750 and this is required margin

  3. Check your current margin blocked for the trade:

I cannot figure it out how to calculate the last bit ???