Wall with Brick Ledge Thickness

[Browneye]

I am using Home Designer Pro 2021.  I designed my home in the software and then had a professional draw up my plans.  Now I want to take the small changes they made and update my plans I built as they made rooms slightly larger or smaller.  My problem is that I cannot get their dimensions to match my dimensions.  I make all the interior rooms match but then the exterior dimesions don't match. I call them and asked what depth they use for a brick wall thickness.  My focus is a 2x4 stud wall with brick.  They said their brick ledge is 5 1/2" and the total wall thickness is 9 1/2".  They didn't seem too eager to help me understand any more detail than that.  I've looked up typical brick depths and see 3 1/2" and 3 5/8 brick depths are normal.  Even with a 3 5/8" brick depth, my total wall thickness in the software is only 9 1/16" inch (3 5/8" brick, 1" air gap, 7/16" OSB, 3 1/2" stud, and 1/2" drywall).

Question 1 - Why does the software say this wall thickness is 9 1/16" but if you add those figures together, it comes out to 9 1/8" (see attachment).

Question 2 - How is a brick ledge considered 5 1/2" (including 7/16" OSB, 1" air gap, and brick)?  Assuming 3 5/8" brick, isn't that only 5 5/16"?  Where is the other 3/16" coming from?

Question 3 - When you look at exterior dimensions of a professional drawing (attached).  Are those exterior dimensions actually from the outside of the brick or the outside of slab?  Maybe they should be the same but didn't know if some bricklayers use an overhang or something that might be the dimension difference? 

[y-g-m-n]

when they make the forms they use a 2x6 and lay flat to create the brick ledge which is 5.5" wide..

Much cheaper then ripping them to make it thin

 

But wall layers should be 

brick = 3.5"

Air Gap= Min 1.5"

Sheathing = ~1/2" (15/32" plywood or 7/16" OSB)

----- Brick Ledge Edge ------

Stud = 3.5"

Sheet Rock = 1/2"

 

So stuff on brick ledge side = 3.5+1.5+.5 = 5.5"

 

 

Just adjust your air gap to create wall thickness to match so your plans match.

Around here, some builders putting up 1/2" foam board to sheathing and taping joints so air gap goes back to 1" - $$$ but helps with Thermal break and insulation