Thanks for the reference and update on how waypoints are given their naming conventions. Both FS9 and FSX use the AIM's and the ARINC424 Documents where applicable.
We can look at many of the stock waypoints / T_waypoints in FS and see some of the same naming that your link shows. Here is a quote from the link document.
D stands for DME arc waypoint. Aaa is the radial that the fix is on from the reference VOR. B will be a letter corresponding to the distance from the reference VOR. For example, G is the seventh letter of the alphabet so D234G would be a point on the 234° radial 7 nm from the reference VOR. DME arcs greater than 26 nm will have waypoints where the first two characters are the first two letters of the DME identifier. The next three characters will be the radial that the arc waypoint is on.
If I look at a typical DME arc in FS using the ADE Approach Mode Editor I would see a IF (Intial Fix) unnamed terminal_waypoint D016P. This tells me the IF is a DME arc waypoint, it is 16 NMs from the VOR and the P is the 16th letter of the alphabet.
In the next picture the DME arc continues to the Terminal_Waypoint unnamed D336P. This is the AF leg type which has all the ARINC 424 Document data.
P is the 16th letter of the alphabet so D336P would be a point on the 336° radial 16 nm from the reference VOR.
In the following picture I use the helper distance line (red) to confirm the placement of the D336P Terminal_Waypoint. It shows (from the VOR) the length of the line is 16NM - heading 342 True / 336 Mag
The AF leg type must have the following in order for the arc to draw properly.
Fix Type = Terminal_Waypoint
Fix Region = K3
Fix Ident = D336P
Turn Dir = Left
Recommended Type = VOR
Rec Region = K3
Rec Ident = HUT which is the VOR Ident
Theta Deg = 336 Mag which is the degree from the VOR
rho NM = 16 which is the distance from the VOR
Course Type = Mag
Course Deg = 16 and this tells us where the magenta line you see starts. This is the entrance point to the DME arc.
If we were to draw a helper line from the HUT VOR on a heading of 16 Mag Deg it would extend just to the left of the IF D016G terminal_waypoint.
If I was updating this DME arc I would increase the Course deg to something like 20. This would lengthen the magenta line entrance point so it is exactly at the D016P Terminal_waypoint.