If calculated value column exceeds 24 hours

O365Developer 

I'm kinda new to this, where in my code should I input this code?

Did like example below, doesnt work. Guess its all wrong

{
  "$schema": "<a href="https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json" target="_blank">https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json</a>",
  "elmType": "div",
  "attributes": {
    "class": "=if(@currentField <= '02:00:00', 'sp-css-backgroundColor-successBackground50', if(@currentField >= '02:00:00', 'sp-css-backgroundColor-errorBackground50', '"
  },
  "children": [
    {
      "elmType": "span",
      "style": {
        "display": "inline-block",
        "padding": "0 4px"
      },
      "attributes": {
        "iconName": "=if(@currentField <= '02:00:00', 'CheckMark', if(@currentField >= '02:00:00', 'Warning', '"
      }
    },
    {
      "elmType": "span",
      "txtContent": =@currentField > 24 ? 'Over 24 hours' : @currentField
    }
  ]
}