What is _data in object received from firestore?

I'm using firestore in my react native app.In some case I calling firestore to get all docs from specific collection and for some reason the array of data received in wrong format.

{"_data": {"clinicAddress": "1", "clinicName": "Macab", "description": "Nice doctor I think", "docs": [], "doctorName": "Caaw", "timestamp": 1652290939, "title": "Check my ears"}, "_exists": true, "_metadata": {"_metadata": [false, false]}, "_ref": {"_documentPath": {"_parts": [Array]}, "_firestore": {"_app": [FirebaseApp], "_config": [Object], "_customUrlOrRegion": undefined, "_nativeModule": [Object], "_referencePath": [FirestorePath], "_settings": [Object], "_transactionHandler": [FirestoreTransactionHandler]}}}

How can I get only the objects inside data?

Here is my interface:

export interface Appointment {  clinicAddress: string;  clinicName: string;  description: string;  docs: any[];  doctorName: string;  timestamp: number;  title: string;}

And this is the function to fetch the data:

export const fetchAppointments = (): Promise<any> =>  new Promise(async (resolve, reject) => {    try {      const data = await firestore().collection('users').doc(auth().currentUser?.uid).collection('appointments').get();      resolve(data.docs);    } catch (e) {      console.log(e);      reject(e);    }  });