Adobe Target Product Recommendaiton: categoryID in Feed File

We have been getting ready to upload product data into Target for Product Recommendation using the csv approach.

According to documentation, we need to populate entity.categoryId as a comma separated value. But this is confusing because csv is comma separated, and the comma separated values get pushed into the next column. So, the second categoryId would get pushed into the next column which in our case is imagelink and so on.

What is the recommended approach to updating the entity.categoryID field when using csv file?  For other custom attributes with multiple values, we are using arrays with [], should we do this here too?