My 323 was also documented by a previous owner, but it has lapsed and I don't have the details (there have been 8 POs!)
I just went through the USCG "Simplified" rules for calculating gross tonnage, using estimated measurements from memory, and came out with a Net Tonnage (NRT) of 9!!!
This is so far above the required 5 minimum that either I'm WAY off on my numbers, or they are wrong on your application.
For reference, here's the numbers I used. Refer to the "Simplified Measurement Tonnage Guide 1" (
https://www.dco.uscg.mil/msc/tonnage-guides/) pages 7-9:
Hull Volume = S x K x L x B x D = 825
-------------
S = 0.5 (shape factor for sailing hulls)
K = 0.75 (keel factor for sailing hulls)
L = 32.25
B = 10.5
D = 6.5 (toerail to bottom of keel)
Deck Structure Volume = Ls x Bs x Ds = 127
--------------------------
Ls = 15 (average length)
Bs = 8.5 (average width)
Ds = 1 (average height)
Gross Tonnage (GRT) = trunc((Hull + Deck) / 100) = 9
------------------------
Hull = 825
Deck = 127
Net Tonnage (NRT) = trunc(M x GRT) = 8
--------------
M = 0.9 (Machinery factor for vessels designed for sailing with propulsion machinery inside the hull )
Now, admittedly, my estimates for the deck structure dimensions and depth (D) are pretty approximate, but even if I set the Deck Structure volume to ZERO, and reduce the depth to 6, It still comes out to A GRT of 7 and an NRT of 6!!
It sure looks like there's an error in the numbers they used in calculating your application.
Please feel free to point out any errors in my numbers. I won't be offended.