Spawn Entity

Hi, in my mod I have this code in my Pre-Init method to spawn my mob:

 

EntityRegistry.addSpawn(EntityLostSoulMob.class, 120, 2, 5, EnumCreatureType.monster,BiomeGenBase.beach, BiomeGenBase.desert, BiomeGenBase.extremeHills, BiomeGenBase.forest, BiomeGenBase.jungle, BiomeGenBase.plains, BiomeGenBase.taiga, BiomeGenBase.taigaHills, BiomeGenBase.frozenRiver, BiomeGenBase.frozenOcean, BiomeGenBase.swampland, BiomeGenBase.extremeHillsEdge, BiomeGenBase.extremeHills,BiomeGenBase.forestHills, BiomeGenBase.hell, BiomeGenBase.sky, BiomeGenBase.icePlains,BiomeGenBase.mushroomIsland, BiomeGenBase.mesaPlateau);

although 120 is apparently very high this makes the mob spawn at good amounts, less than all the other mobs (creeper, zombie, etc.) When I'm only playing my mod this number is alright, but when I added it to a modpack to try it out they started spawning at incredibly large amounts. What is a good number to have the weight at so its balanced. And what factors could make my monster spawn uncontrollably?