Can a bonus be too small to use?

If your bonus amount isn't large enough to sustain the funds-to-bonus ratio when you open a trade, due to the bonus being too small or the trade amount being too large, your entire bonus will be used, and the remaining amount will consist of your real funds.

If the trade is successful, the profit will be split between your bonus and real funds in the same proportion that was used to open the trade. Losses due to unsuccessful trades are calculated in the same way.