Why does -1000 >= -1000 get interpreted as false in this code?

So I almost fully understand methods, objects and OOP. However I was working on an exercise in a German Java programming book for beginners where I had to create a bank account with a withdraw limit of up to -1000 euros. Somehow, even though the amount is -1000 euros, the code executes the else code, which for me makes little sense. It shouldn't output the error in my opinion, but it does.

Here is the account code:

public class Account {
  private String accountnumber;
  protected double accountbalance;

Account(String an, double ab) {
  accountnumber = an;
  accountbalance = ab;  
}

double getAccountbalance() {
  return accountbalance;
}

String getAccountnumber() { 
  return accountnumber;
}


void deposit(double ammount) {
  accountbalance += ammount;
}

void withdraw(double ammount) {
  accountbalance -= ammount;
}

}

The extended account:

public class GiroAccount extends Account{

double limit;

GiroAccount(String an, double as, double l) {
  super(an, as);
  limit = l;
}

double getLimit() {
  return limit;

}

void setLimit(double l) {
  limit = l;

}

void withdraw(double ammount) {
  if ((getAccountbalance() - ammount) >= limit) {
    super.withdraw(ammount);
} else {
    System.out.println("Error - Account limit is exceded!");
}

}

}

The code to test the accounts:

public class GiroAccountTest {

public static void main(String[] args) {
   GiroAccount ga = new GiroAccount("0000000001", 10000.0, -1000.0);
   ga.withdraw(11000.0);
   System.out.println("Balance: " + ga.getAccountbalance());
   ga.deposit(11000.0);
   ga.withdraw(11001.0);
   System.out.println("Balance: " + ga.getAccountbalance());

}

}

The output:

Balance: -1000.0
Error - Account limit is exceded!
Balance: 10000.0

Also the original code is written in German so I hope my translation of the code is easy to follow! :) Thanks in advanced for the help.