Signs Are Meant to Communicate

I live in St. Paul, Minnesota, a city whose streets were laid out by drunken Irishmen (according to our former governor, Jesse Ventura).

I'm not sure if that included the city's parking restrictions.

I encountered these tandem signs on a Saturday afternoon while cruising down a side street near the Minnesota History Center. Was it legal for me to park there?

I still have no idea, even though I did it, reasoning that I could argue to a judge that if two-hour parking was allowed Monday through Friday, it was reasonable to assume it was also allowed on Saturday, since parking restrictions are usually more lax on weekends, if anything, rather than more stringent.

And what the heck does "exempt" mean in this context? Is that word intended for the public to understand, or is it a secret code for the meter maids?