I have this structure:

Object { cid: "c130", attributes: {…}, collection: {…}, _changing: false, _previousAttributes: {…}, changed: {}, _pending: false, _lastTeamSession: false, _events: {…}, _listenId: "l131", … }
​
_changing: false
​
_events: Object { all: (1) […], change: (1) […], destroy: (1) […], … }
​
_lastTeamSession: false
​
_listenId: "l131"
​
_listeners: Object { l32: {…}, l133: {…} }
​
_pending: false
​
_previousAttributes: Object { duration: "00:00", value: 5, format: "1", … }
​
attributes: Object { duration: "53:04", value: 5, format: "1", … }
​​
athlete: Object { cid: "c11", _changing: false, id: 6, … }
​​
duration: "53:04"
​​
format: "1"
​​
teamsession: Object { cid: "c8", __version: 43, _changing: false, … }
​​
value: 5
​​
<prototype>: Object { … }
​
changed: Object { duration: "53:04" }
​
cid: "c130"
​
collection: Object { length: 1, models: (1) […], _listenId: "l31", … }
​
<prototype>: Object { … }

As you can see in attributes I've duration key, and its value is "53:04".

I want to assign this value to a variable using: let duration = this.model.get("duration");, but I obtain that duration's value is "00:00" and I don't understan why... Can anyone help me?