If there is only one firmware version listed, it means that only one firmware version has been ported to CHDK.
That could mean that there is only one firmware version released by Canon for that camera.
However, it could also mean that there are several versions but only one has been ported to CHDK.
In most cases, the ported version will not work on any other firmware version. Although there are exceptions to that rule.
There is no way to tell for sure, especially on a newer camera models.