I don't see an error either. The port lists have to be the same length (i.e. the range has to be the same amount of ports) but they do not have to be the same ports. 8080 to 80 is two lists of one port. Since both list are one port they are the same length.
The example has 8000-8500 to 8000-8500, which it two lists of 501 ports.