Tire size question. What is the 8 in 17LT/8??

On the Mickey Thompson Baja MTZ 33X12.50R17LT/8 tires, what is the "8" for? I was wanting to buy these tires to go on my 17x9 rims. Is the 8 relevant to that? Sometimes it R17/8 and sometimes its R17LT/8.

 

LT refers to light truck. Perhaps the 8 means 8 ply?

 

Mickey Thompson doesn't even list that tire followed by the 8...in fact most websites don't. One of the few that does is Walmart (which seems to be the best price.) They are 3-ply sidewalls, load range D, and speed rated at 114Q. They are all the same part number (5273) no matter if the site mentions 8 or not. I think it's immaterial. Unless it stands for 8 mpg...which is what you'll likely get.