Mqtt rollershutter commands

Hi
I have integrated a bticino roller relay with z2m
The three commands (up, down and stop) work well, but when I try an opening percentage nothing happens


example: the command that is sent is simply 90 instead of { “position” : 90} that would work

UID: mqtt:topic:3f31d0c4ed:2d8a798a3b
label: Tapparella Salotto
thingTypeUID: mqtt:topic
configuration: {}
bridgeUID: mqtt:broker:3f31d0c4ed
channels:
  - id: Rollercontrol
    channelTypeUID: mqtt:rollershutter
    label: Roller control
    description: ""
    configuration:
      postCommand: true
      invert: true
      transformationPatternOut:
        - '{ "position" : %s}'
      qos: 0
      stop: '{"state": "STOP"}'
      commandTopic: zigbee2mqtt/Tapparella_Salotto/set
      transformExtentsToString: false
      stateTopic: zigbee2mqtt/Tapparella_Salotto
      transformationPattern:
        - JSONPATH:$.position
      off: '{"position": 0}'
      on: '{"position": 100}'

this is my configuration, i need this functionality for google and alexa implementation,
i have also tried formatBeforePublish: ‘{ “position” : %s}’ but with the same result