All contracts are settled in the settlement coin (USDt). All fees, including withdrawal fees, are charged in USDt as well. It is therefore important that you maintain sufficient USDt in your account.
If your account's USDt balance is positive, you can withdraw any of your assets, provided that your total account balance remains higher than your margin requirement.
If your account's USDt balance goes negative, Thalex deducts 25% of that negative balance from your withdrawable account balance. This means that if your USDt balance reaches -1000, you can only withdraw other assets up to a limit of your margin requirement + $250. This applies on an account level and affects withdrawals and transfers between accounts.
This reduction in withdrawable balance is in force as long as your USDt balance is negative.