I can't answer your question with any authority, but I'll share my thoughts and provide context. You probably already know some of this, just trying to cover all bases. Drawing heavily from two webinars presented by Emily Guglielmo: SEA-MW September 2021 Meeting, and Session 1 of AISC Night School 29, which was two weeks ago.
Note 6 is a mess. Breaking it down:
Coefficients are for roofs with angle theta <= 7 degrees. <This tells us that we're here because our roof slope is less than 7 degrees, which is a funny thing to say to someone you just sent here for exactly the opposite reason (notes 3 and 4 on 30.6.1 are for roof slopes greater than 7 degrees).> For other roof angles and geometry, use GCp values from Fig 30.3-2A-2I and Fig 30.3-5A,5B... <This tells us where to get GCp values, which Part 4 doesn't use.> ...and attendant q_h... <This is to make sure we're using q_h, which Part 4 also does not use.> ...based on exposure defined in Section 26.7. <Linking back to the definition of Exposures B, C, and D in Ch. 26.>
If we were using Part 3, we would have been referred here by section 30.5.2, which tells us where to get our GCp values for walls and flat roofs from T30.5-1, and refers us to Note 6 for any other geometries. Part 4 is the simplified method based on Part 3 equations and coefficients. Since we're using Part 4, none of this is directly applicable.
My take is that the Part 4 authors are referencing this note to document how they got the tabulated values. Parts 1 and 3 have a paper trail of section references to textbook definitions of exposure categories and "h", but not Part 4. I think this note is a reminder that you're supposed to know that exposure is per section 26.7, and height should be the Chapter 26 definition you would use for q_h: "h = mean roof height of a building or height of other structure, except that eave height shall be used for roof angle theta less than or equal to 10 degrees, in ft (m)."
That's the best apologetics I can come up with, but it's still a bad look for 7-16. Even if I'm right, this should've been in the commentary not the code. What do you think?
Here is the code logic I would follow for this problem in ASCE 7-16:
1. Equation 30.6-1 refers us to Table 30.6-2 for EAF, RF, and p_table.
2. Table 30.6-2 notes 3 and 4 refer us to Table 30.4-1 for pressures because our slope is low, but remind us to use the roof zones from T30.6-2, on the previous page.
3. Because of notes 3 and 4, Note 5 also applies. This is a heads up that Table 30.4-1 will try to gaslight us into using its lambda values, but we shouldn't listen to it. Lambda shall be from T30.6-2, ignore the siren song and stay the course.
4. We're going to need a roof height to get our pressure out of Table 30.4-1. Notes 3 and 4 also directed us to Note 6 in T30.5-1, which wants us to close our eyes and pretend we're looking for q_h so that we realize that "h" is the eave height, not the average.
5. Check the exposure category definitions in chapter 26 and pick one. Now we can flip to Table 30.4-1 to get that pressure, which T30.4-1 calls p_net30.
6. Sure enough, T30.4-1 note 1 refers to eq. 30.4-1, which in turn references back to T30.4-1 for lambda. Note 5 in T30.6-2 warned us about this so we'll ignore it and get lambda from pg 367 instead.
7. We need p_table for eq. 30.6-1; Note 5 from T30.6-2 tells us this is actually lambda x p_net30 from 30.4-1. In your case p_table = 1.676 x -48.5 psf = -81 psf.
8. Luckily we're Exposure C, because otherwise we would have to multiply in the Exposure Adjustment Factor from pg. 366. Note 1 under the EAF table lets us off the hook. Whew!
9. Luckily our effective wind area is 10', so RF = 1 for all Exposure Categories.
10. That does away with all our terms in eq. 30.6-1 except for K_zt. If our topo is normal, our design pressure ends up being the same 81 psf as p_table.
In my opinion, there is nothing simple about this "simplified" method. ASCE 7-22 authors seem to agree: they removed Parts 2 and 4 from Chapter 30, reducing the C&C page count by a third. My advice is to use Part 3 instead: it's more accurate and harder to mess up. I have never met an engineer who uses the simplified methods regularly, but I would be interested to hear from anyone who does.