potentialspawn.json

[
  {
    "dimension": -1,
    "mobs": [
      {
        "mob": "minecraft:wither_skeleton",
        "block": ["minecraft:netherrack", "minecraft:nether_brick", "minecraft:soul_sand"],
        "weight": 50,
        "groupcountmin": 2,
        "groupcountmax": 4
      }
    ]
  }
]