Are you saying there are currently 18 active fires in ND ?
I don't know the required size, or time scale, for placing an icon on the map for a fire. I do know that up until the big rains of a couple weeks ago there were about 10 fires per day reported to the State. Even during the heavy rains out west, the eastern part of the state was still having fires with 3-5 reported a day. Many are/were quite small, ranging from a couple of acres up to a couple hundred. Since it's a map produced by Canada, it wouldn't surprise me if there's something of a lag in their inclusion of fires in the United States.
Some of the bigger fires I know of in ND this spring were up in the Belcourt area, but I thought they were in the Turtle Mountain area, not SE of Belcourt.
There are also several relatively large fires in western ND from earlier this spring that aren't on the map, in particular I know of a large one north of Watford that basically burned its way north to the shore of Sak that isn't on the map. I'm pretty sure that one was several thousand acres. My friend's son has been up there replacing fences for a while now.
Probably the worst thing about these damn Canadian fires is that even large rains don't put them out. They will get tamped down, but then just flare up again sometime after the rains are over.