String compareTo understanding

I have a quick question about comparing two Strings. these are my Strings:

String s1 = "bc";
String s2 = "bb";

My understanding is that s1 < s2 because c comes after b in the alphabet. So
s1.compareTo(s2) should return -1. How ever if I test this with System.out.println(s1.compareTo(s2)); it return 1. So what did I understand wrong?

String compareTo understanding