Cannot read properties of undefined in LWC

Hi everyone! I have to get the response from an API Endpoint and display them in a data table (LWC). The response look like this:

"list": [
        {
            "projectName": "Onnami",
            "point": {
                "min": 9.11,
                "max": 9.18,
                "default": 9.11
            }
        },
        {
            "projectName": "Sunshine INC",
            "point": {
                "min": 9.11,
                "default": 9.11
            }
        }
]

I got no problem when getting the "projectName", but when I try to get the "default" key in "point". I get the error: Uncaught (in promise) TypeError: LWC component's @wire target property or method threw an error during value provisioning. Original error:

Here is my client side controller:

import { LightningElement, api, wire } from 'lwc';
import getSubmissionRecords from '@salesforce/apex/SubmissionController.getSubmissionRecords';
const columns = [
    { label: 'Project Name', fieldName: 'projectName' },
    { label: 'Points', fieldName: 'point', type: 'number' },
    { 
        label: '', 
        fieldName: 'details', 
        type: 'url',  
        typeAttributes: {
            label: { 
                fieldName: 'detailName' 
            },
            target : '_blank'
        }},
];
export default class PricingTab extends LightningElement {
    @api recordId;
    @api columnData;
    @wire(getSubmissionRecords, { projectId: '$recordId' })
    returnedSubmissions({data, error}) {
        if(data) {
            let dataRefer = [];
            data.forEach((record) => {
                let preparedData = {};
                preparedData.projectName = record.projectName;
                preparedData.point = record.point.default;
                preparedData.detailName = 'Details';
                preparedData.details = 'https://google.com';
                dataRefer.push(preparedData);
            })
            this.columnData = dataRefer;
        }
        if(error) {
            console.log(error)
        }
    }
}

Here is the HTML file:

<template>
    <lightning-datatable key-field="Id" data={columnData} columns={columns}></lightning-datatable>
</template>