How is that weird, it's just uses the increment from the first to second value as step and repeat as long as it's smaller than the end value. Python does the exact same thing:

    Python 2.7.1 (r271:86832, Jul 31 2011, 19:30:53) 
    [GCC 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2335.15.00)] on darwin
    Type "help", "copyright", "credits" or "license" for more information.
    >>> range(1, 10, 2)
    [1, 3, 5, 7, 9]