@Nielsen Ugh..You're gonna kill me.  I forgot that I disabled almost all of my 3rd party apps, so I only had the Kunos tire app available which doesn't give a numeric wear percentage - there is a color indicator that drops and changes color.  Green good ---> all the way down to Red bad!  But I would have to say that my tires would have been at 0% wear or maybe 0% wear in the back and 1% in the front.  Oh, I did two laps and I forgot to put the surface onto Optimum 100%, I had it on Fast 99%, that probably has no effect on this.  My 2nd lap was faster than my 1st lap by 4-5 seconds - 8:01.444 2nd lap time (if anyone laughs at my lap time I will punch you in the testicles 

).  I only put the lap time to give you an idea of how hard I was pushing it and to be honest, this is pretty much me at the limit in that car with completely stock setup.  I messed up in a couple of areas badly...I definitely lot a few seconds because of the two mistakes.  Anyway, You'll see I had 7% grain on both front tires, 2% grain on both rears.  0% blistering all-around.
Now, I discovered that PC players -- at least, not on my system -- we can't just pull into the pit area and pull into a rectangle to adjust settings in Hotlap Mode.  I didn't try Practice though...I will.  The rectangle doesn't even show up like it does when I'm racing.  I discovered this on a different track as on the Nordschleife I would have had to do another 8 minute lap to get to the pit entrance.
So, after that second lap, I pulled over right before that first left-hander on the Green Hell.  I parked for a couple of seconds and cursed myself for not breaking 8 minutes and I had to do the ESC key - Go To Pits.  That's where I took the screen shot you can see.
I then hit the icon to let me drive again and pulled out of the pits.  I went around that first left-hand turn and came to a stop before I even got to the next right-hander.  I came to a stop, hit ESC, and selected Go To Pits.  When I did my tires were all 0%/0% -- brand new.
So, that definitely leads me to believe that this is yet one more bug plaguing the console version.  I had a very strong feeling it was the second you told me, but I wanted to double-check just to make sure.  I can't remember if I mentioned this was 100% stock setup too.
I don't know if you're into doing races against the AI.  But if you don't mind... Select a smaller track.  Run a handful of laps, and go back to the pits so you can see your setup info like in my screenshot.  Take a note of graining % / blistering % and wear %... I'm pretty sure you don't have to get new tires, but you could try it with getting new ones and then pull over after a couple of corners, like you did to start this conversation and get back to the pits/setup screen to see if you're getting stupid data again.  I'm just curious if this is a problem that is restricted to Practice/Hotlapping or if it also plagues console players in Race Mode too.
I'm sure we can all agree that you don't want to be putting on a fresh set of tires during a race, pull out of the pits and be starting on tires with 10% graining (I think yours were at 10%, if I remember correctly).  I'll still run the Ferrari FXX K later today - just for the heck of it - I'm sure the results will be the same.  But it sure seems like Bug #637 for the Console Version. 
EDIT:  Just so you don't feel all alone in tires not being exactly perfect.  I'm sure we'd all agree that I probably had 7% graining from understeering like a punk... I know.... I know... Anyway, through two entire laps on Nordschleife my front tires never got into the Green (temp).  They stayed Blue.  That means I never got them into "optimal operating temperature".  Now, some people could counter and say "Well, add camber..." and maybe that's true, but I should be able to run the stock alignment and get optimal operating temperature, even if it takes me an entire lap.  And since I probably was understeering a bit, even though I showed no blistering, you'd think those understeers might throw a little more heat into the tires.  But, I never even saw them turning blueish-green. 

  I'm going to try again but drop the front tire Air Pressure by 2 PSI.  I noticed the front tires are 2 PSI higher than the rears in the default setup.  Maybe that'll help... ::shrug::
If you'd like me to try anything else -- just ask... 👍