How may i do two mutations on cards, using just one "play"?

Hey Amanda, how are you? 

To run multiple mutations you need to name each mutation like this: 

mutation {
 m1:updateCardField(
    input: {
      card_id: 383932000
      field_id: "test"
      new_value: "this a new value"
    }
  ) {
    card {
      id
    }
  }

  m2:updateCardField(
    input: {
      card_id: 383932138
      field_id: "teste"
      new_value: "another value"
    }
  ) {
    card {
      id
    }
  }
}

Hope it helps you ;)