Cannot post rules with location capabilities

@orangebucket

Following this thread I´m trying to use some of these values in a rule to write to a tile (using @Mariano_Colmenarejo ‘s Number Field from his Virtual Devices) to compare with my home AirQ sensor values. Triggering from changes in location UltraFineDust value I can write without problem from my PM2.5 dust sensor but can’t find the syntax to write the location value. Unable to see how to use `LocationAttribute’ string you mention here - don´t know if there are any examples or documentation anywhere.
Trying as an alternative on a text field the rule is accepted but, logically being numeric fails - on the API browser Execute button it shows failure but I do see the values, so they are being retrieved. Any ideas on this one? Thanks

The code I’m trying, but the API browser returns “operand not valid for operation” is

{
   "if": {
    "changes": {
     "operand": {
      "location": {
       "locationId": "MY LOCATION ID",
       "attribute": "UltraFineDust",
       "trigger": "Always"
      }
     }
    },
    "then": [
     {
      "command": {
       "devices": [
        "221eb0e5-a898-4f7e-b8cd-e0329371d7e8"
       ],
       "commands": [
        {
         "component": "main",
         "capability": "legendabsolute60149.numberFieldOne",
         "command": "setNumberFieldOne",
         "arguments": [
          {
           "device": {
            "devices": [
             "MY PM2.5 SENSOR ID"
            ],
            "component": "main",
            "capability": "fineDustSensor",
            "attribute": "fineDustLevel"
           }
          }
         ]
        }
       ]
      }
     },
     {
      "command": {
       "devices": [
        "221eb0e5-a898-4f7e-b8cd-e0329371d7e8"
       ],
       "commands": [
        {
         "component": "main",
         "capability": "legendabsolute60149.numberFieldTwo",
         "command": "setNumberFieldTwo",
         "arguments": [
          {
           "location": {
            "locationId": "MY LOCATION ID",
            "attribute": "UltraFineDustIndex"
           }
          }
         ]
        }
       ],
       "sequence": {
        "commands": "Serial",
        "devices": "Serial"
       }
      }
     }
    ],
    "sequence": {
     "then": "Parallel",
     "else": "Serial"
    }
   }
  }