In the documentation for @@Options in Books Online, it states that "The result is 1010101111000. The left most characters (binary 1, 2, and 4) are 0, indicating that IMPLICIT_TRANSACTIONS and CURSOR_CLOSE_ON_COMMIT are off. The next item (ANSI_WARNINGS in the 1000 position) is on. Continue working right though the bit map, and down in the list of options. When the right-most options are 0, they are truncated by the type conversion. The bit map 1010101111000 is actually 001010101111000 to represent all 15 options.".
I believe that the directional verbiage is backwards and that it should read that the right most characters (binary 1,2,4) are 0 and that the when the left most characters are zero that they get truncated off by the type conversion.