https://openjicareport.jica.go.jp/pdf/11156205_01.pdf#page=39 Greetings according to MOP:
"Primeramente, es importante señalar que el número de rutas será asignado a la provincia **que parte** de la carretera cruce de una provincia a la otra. En segundo lugar, que la parte de la vía sea mayor en longitud dentro de la Provincia"
Since the highway *starts* in Chiriquí, it receives this road numbering, that reason why Highway 4099 also it's present in the comarca, because they start there.

Unless I'm missing something, sorry, I only have some maps for Chiriquí, it shows the highway as 40, feel free to revert some of my changes, I tend the put the sources with the MOP maps I have. Do you have any source for Highway 12, I don't have maps for this comarca unlike some parts of the province.
https://alairelibre.net/mapas/Mapas/tole3840-I.jpg

Unfortunately there is very little content of the M Routes online, those are used to represent the various Expressways. But recently UNRA and KCCA have installed signs marking the M routes (https://archive.ph/gahHR & https://archive.ph/fmOPk <- Images from 2025 showing signs showing the M3/Entebbe Expressway).
At the moment the entire M3 has already been marked by UNRA (See image: https://x.com/kiyagaedwin/status/1691133674807349265) and several road sign design representatives such as Kiyaga Edwin Raymond (Senior Highway Design Engineer at MowT) on Twitter have indicated that they are designing and preparing for the installation of road signs on the interchanges in Kampala including several intersections of the Northern Bypass (M20) and Southern Bypass (M21). (See proposed Kisaasi Interchange signage design (https://x.com/kiyagaedwin/status/1756218002431758754/photo/1) showing M20 and M21 marked). I am talking to them if they can give us an official document containing information about the M Routes.
-- DigitalSeb01

Hi, ChromeLotus. I recommend consulting the Aaroads Wiki (https://wiki.aaroads.com/wiki/Category:Uganda) for more information. We recently had discussions to include alphanumeric codes to the Ugandan routes (https://wiki.aaroads.com/w/index.php?title=AARoads:The_Interchange&oldid=568002#Uganda_Road_Numbering)
Sources:
* https://openjicareport.jica.go.jp/pdf/12013058_01.pdf (Page A1-21)
* https://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433/283688/5/dkogk05075.pdf (Page 57)
These codes appear on the signs from 2022 (This can be confirmed by user photos showing that this road is coded A5 to the DR Congo border):
- https://x.com/PJafali/status/1502172731499941896
- https://x.com/RasBSsali/status/1826732565958721914
-- DigitalSeb01