Maps with multiple Breaches gives only 2 or 3 Breach Spinter in POE2

Since I apply "contain multiple breaches" waystones, some of the Breaches gives surprisingly low amount of Breach Spinters, even the Breach is open for a long time and plenty of monsters are killed within it.
Breaches with the same uptime gives 10-17 Breach, even on the same map, even after the first 2 Breach Spinter giver Breach cleared most of the normal monsters from the map.