Hopefully Linguistics Can Save Me Now

So, last night I was driving around a campus that I am not very familiar with, especially where I am allowed to park as I have no affiliation with the university. I was told that there was a main road that I would probably be space on. The signs along this road all read something more or less:

Student/Staff Parking 6AM-1AM NO PARKING 1AM-6AM

All of the signs along the road were very clear. So I figured it was best to keep looking around. Apparently there is a visitor lot that I managed to miss because it was late and the sign was not well lit, and was a distance from the road. I arrived at a lot that had the following information on the sign:

Staff Parking 6AM-1PM Student Parking 1PM-4PM

There was no mention of what is going on between the hours of 4PM-6AM. I am familiar with another university that has similar signs, and anyone can park during the unlisted hours, since there is no longer a premium on parking. Apparently, to my dismay, the implication of this sign is that there is not to be any parking in this lot during the unmentioned hours. Of course, now I need to pay the university because they didn't explain to me where I am allowed to park. I probably won't contest it, it's not very much money, but does anybody think I have a case?