When you view your balance, the top amount is the total amount you can use for betting on your account. However, this is not necessarily the amount you are able to withdraw, as parts of the funds could be blocked due to incomplete bonus requirements being met.
The liquid funds show you the amount you are able to withdraw without any bonuses being cancelled. If the maximum withdrawal amount differs from the liquid funds, this means that you can request a withdrawal up to that amount, but by doing so some open bonuses could be cancelled. You will be warned about this during the withdrawal process.