question

It looks like you want to create a region selection rule about matchmaking. First, you need to add a Region selection rule when you configure the matchmaking queue.

And here is a sample of how to add latency to Matchmaking Ticket.

 POST https://{
                 {TitleId}}.playfabapi.com/Match/CreateMatchmakingTicket 
  {
      "Creator": {
          "Entity": {
              "Id": "A8140AB9xxxxxxx",
              "Type": "title_player_account",
              "TypeString": "title_player_account"
          },
          "Attributes": {
              "DataObject": {
                  "mu": 16.0,
                  "sigma": 1.8,
                  "Latencies": [
                      {
                          "region": "EastUs",
                          "latency": 150
                      },
                      {
                          "region": "WestUs",
                          "latency": 400
                      }
                  ]
              }
          }
      },
      "MembersToMatchWith": [],
      "GiveUpAfterSeconds": 60,
      "QueueName": "TestQueue"
  }

Please note that the "Latencies" (which in Region selection rule) must match the "Latencies" of Attributes in CreateMatchmakingTicket. For more details, please refer to Region Selection rule.