Leveraged positions are automatically closed at their given liquidation price (that you can see in the positions detail panel). Read our page about leverage and margin for more details.
The maintenance margin required is about 20%, which is why the liquidation price level is often set to trigger once your position reaches 80% loss. This is to guarantee that your position can be closed in time to cover your margin, especially in fast-moving markets. Most brokers have 30% maintenance margin requirement, but Whaleclub only requires 20%.
This is done to prevent the amount of money you owe, including your margin, from going negative (below 0). Whaleclub has an isolated margin system, which means that each position's margin and liquidation price are fixed and calculated individually.