A cursory glance at OpenStreetMaps shows that both the Kurskaya Oblast and the Bryanskaya Oblast border Ukraine directly. Car direction routes from the centres of the towns mentioned to what seems to be the closest road border crossing to Ukraine clock in at around 112 km (Kursk) and around 144 km (Bryansk) (sadly, the links do not include the route itself).
Concerning Yelnya, the article puts it 'near the Belarus border' which seems equivalent at 114 km to Belarus. Yelnya is in the Smolenskaya Oblast which borders Belarus.
The distances to Moscow are approximately 371 km (Yelnya), 527 km (Kursk) and 383 km (Bryansk).
I wasn't able to discern why the article mentions the units apparently deployed to Yelnya and what the Belarus border has to do with any of this. However, units gathering around 100 km from a border by road – especially in a country as large as Russia – does suggest that this is something to keep an eye out for and a potential cause for concern. This seems like a good 'first gathering' distance: close enough to get there quickly yet far enough to not be in immediate danger – and being near larger cities is likely beneficial for supply purposes.
That said, the article mentions 'areas around Kursk/Bryansk', so how close it is to the cities and the actual distances to the borders are not immediately obvious. Indeed, from glancing at OpenStreetMaps it seems like these two are the only larger towns in their respective oblasts so 'area around' could technically mean anywhere in the oblast.