{
  "$schema": "https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json",
  "elmType": "div",
  "children": [
    {
      "elmType": "div",
      "style": {
        "font-size": "15px",
        "visibility": "=if(floor(@currentField)<1,'hidden','visible')",
        "margin": "5px 0px"
      },
      "children": [
        {
          "elmType": "div",
          "forEach": "iterator in split(padStart('',floor(@currentField)-1,'^'),'^')",
          "style": {
            "margin": "3px"
          },
          "attributes": {
            "iconName": "Contact"
          }
        }
      ]
    }
  ]
}