Well when you say higher priority, you're really saying higher number. Nice and consistent. If higher priority meant lower number that would be slight inconsistent and would make it awkward if you wanted some modules to be higher than all the rest all of a sudden as you'd have to lower them to 1 then raise all the others by 1.
Hmm. Got to say pfft

As far as I can recall, I've not saw a real life example using the system you are describing. I've often heard or even used the expression "what's my first priority, and what's my second" while in that context it's very obvious what is meant, it still carries over to any system that uses priorities. 1 means first and foremost, the top tog, most important everything else follows that.
Various Sci-Fi shows use it as well...
"Priority 1 message captain"
"hmm? I'll get it later"
"but the evil robots are going to kill Earth"
"Priority 1, you said, time for a cup of tea first, no?"
Is something you'll never see. Or Hear.
