How many columns in a wix dataset can be referenced using Velo code?

I've watched several tutorial videos of WixWiz on youtube. Thank you for those helpful videos!

I am trying to help my church create a lending library. The page is not live because eveything in it is broken! I have created a dataset with 9 columns. I understand that there will be system generated columns. However when I am trying to get the columns, I see to get only 4 or 5 columns!

Here is my code:

const bookLoadResult = await wixData.query('Import1').limit(1).find();

        const firstItem = bookLoadResult.items[0];
        // Filter out fields that start with an underscore
        const customFields = Object.keys(firstItem).filter(field => !field.startsWith('_'));
        const numberOfCustomColumns = customFields.length;
        console.log('Number of custom columns:', numberOfCustomColumns);

Here's the result:

Number of custom columns: 4
numberOfColumns 8
bookTableHeaders 
Array(8)jsonTableCopy JSON
0: "author"
1: "_id"
2: "_owner"
3: "_createdDate"
4: "_updatedDate"
5: "bookCopies"
6: "available"
7: "title"

The ordering of the columns are also different. I have tried creating everything I need as a .csv and importing.

Sometimes, the maximum number of columns it seems to fetch is 9(including system generated columns)! What can I do? Or..... Is this because of my payment plan tier?