AirFX is different from margin trading in that it uses an EPS structure that prevents all users from incurring loss on their margin. If EPS is activated, relative to other users who may possibly incur a loss on their margin, an account settlement may occur even if you hold a position with unrealized gains.
Please understand that these forced settlements can occur regardless of whether you did or did not set a limit.
For more on EPS, please refer to the What is Zaif AirFX? article.