SSM Custom Runbook Fails

hi there. I am trying to create a custom runbook containing some other AWS runbooks. I receive the following error:

"Step fails when it is Executing. Fail to start automation, errorMessage: Target key can have only following values : ParameterValues, ResourceGroup or begin with tag:, AWS::EC2::Instance, InstanceIds, instanceids (Service: AmazonSSM; Status Code: 400; Error Code: InvalidAutomationExecutionParametersException; Request ID: kkk; Proxy: null). Please refer to Automation Service Troubleshooting Guide for more diagnosis details."

My Custom Runbook content is:

{
  "schemaVersion": "0.3",
  "description": "*Replace this default text with instructions or other information about your runbook.*\n\n---\n# What is Markdown?\nMarkdown is a lightweight markup language that converts your content with plain text formatting to structurally valid rich text.\n## You can add headings\nYou can add *italics* or make the font **bold**.\n1. Create numbered lists\n* Add bullet points\n>Indent `code samples`\n\nYou can create a [link to another webpage](https://aws.amazon.com).",
  "parameters": {
    "InstanceId": {
      "type": "String"
    },
    "SubnetId": {
      "type": "String"
    },
    "TopicArn": {
      "type": "String"
    }
  },
  "mainSteps": [
    {
      "name": "AWSSupport_CopyEC2Instance",
      "action": "aws:executeAutomation",
      "nextStep": "AWS_TerminateEC2Instance",
      "isEnd": false,
      "inputs": {
        "DocumentName": "AWSSupport-CopyEC2Instance",
        "Targets": [
          {
            "Key": "AWS::EC2::Subnet:Id",
            "Values": [
              "{{ SubnetId }}"
            ]
          }
        ],
        "TargetParameterName": "{{ InstanceId }}"
      }
    },
    {
      "name": "AWS_TerminateEC2Instance",
      "action": "aws:executeAutomation",
      "nextStep": "Publish",
      "isEnd": false,
      "inputs": {
        "DocumentName": "AWS-TerminateEC2Instance",
        "TargetParameterName": "{{ InstanceId }}"
      }
    },
    {
      "name": "Publish",
      "action": "aws:executeAwsApi",
      "isEnd": true,
      "inputs": {
        "TopicArn": "{{ TopicArn }}",
        "Message": "Instance was moved.",
        "Service": "sns",
        "Api": "Publish"
      }
    }
  ]
}

something wrong is with the key of the first run book for copying EC2 instances. for the key, I need subnet not instance. please help.