Dumb Question about Deck Height

Okay, so new guy here. Up until the last year or so ago, my theory on mowing was, "If it's low, it good to go". But, then I started taking an interest in my lawn and how tall I should cut my grass. So, with that being said, I try to keep my fescue around 4" because, well...it just looks better oddly enough than when I cut it at 3.5". So, as a favor to my father-in-law, I sold him my riding lawn mower that I knew was set to cut at 4" at the highest deck setting (I broke out a ruler to verify it) and moved on to a zero turn. This mower as well said that the maximum height cut was 4". I was going to trust the numbers provided by the manufacturer, but just couldn't let it go. So, into the garage I went and pulled out my trusty ruler. On the highest setting, it read 5" to my surprise.

So here's the dumb question part: When I engage the blades, do they get lower, or am I missing something? They do not appear to get lower, nor do I intent on trying to "get close" with the blades moving.

Sorry for the stupid question, I'm still learning the wise ways of the mow.

Thanks!

The numbers are just that, numbers not inches.
The tyre pressure, blades, deck type and grass variety will all affect the actual cut height.
That is why a lot of factories identify the deck positions with letters but some people can just not understand this.
Your push mower might have 10 height settings but no one cares what they actually are, they just adjust them to a height that is good for their grass but the instant they get on a riding mower the numbers HAVE to mean something when they don't.
So same as the push mower adjust the deck to the cut you like best and then remember what number it was.

Thanks for the explanation. My mower has 8 settings, but it just threw me off that there was a 1" difference in what is advertised versus what I actually measured.

Have you dropped the tyre pressure ?
When being transported the tyres are over inflated to gain height & stability when tied down.
Most mower shops will drop they tyres to running pressure when they drop the mower off to you.
Leaving the tyres over inflated can cause them to pop if they are left in the sun and is hard on the spine.

I have not, I'll check the pressure, hopefully today and adjust if necessary.