I'm not sure I get the question. Internally I use some abstract units, I don't scale them for SVG export. For example, if there is a rectangle 10 pixels long in an unscaled SVG, in the model this rectangle is 10 units long as well. Before the scale bar was introduced, I didn't really need to know what were those units. For the scale bar I chose some arbitrary value as the conversion rate which seemed more or less right. But people have different ideas about what should be the average house size or average road width, so I'll probably implement a way to change the conversion rate. Which affects only the numbers on the scale bar.
Viewing post in Question regarding scale
When it generates a map with a citadel, it is of a general size on the map (depending on small/medium/large) .. does the ruler scale make sense for that citadel, or is it suggesting that the citadel is massively huge or ridiculously tiny For example, according to Google Maps, Windsor Castle is about 450m end to end, Chepstow Castle is about 200m, and Dover Castle is about 100m (inner walls, or just 30m if measuring just the keep itself).
For small towns, the citadel building appears to be about 75m; medium towns have citadel castles of ~100m; and large towns have castles of about the same size. These are on the strangely large side.
In my opinion their size is ok. The generator is made with a fantasy setting (and its epic castles) in mind, so generated citadels are larger than average real-world castles, but not unrealistically large. What really bothers me is their design - a single ring wall and a single huge building (a keep?) inside. That's not how most real castles looked, but on the other hand this way they can be very easily identified on a map.
Looking at a few on google maps with satellite view, I see two common patterns: the ring wall with centrally isolated keep, and a ring wall with many buildings barnacled on the interior surrounding an open space.
The open space was usually used to marshall troops, or for huddled masses of refugees (e.g. all the rich bastards from city).