Bulk adding variants, what do I do with the Variant ID field?

Hi.

What do I do with the Variant ID field if I am bulk adding variants to an existing site, the support examples are not clear on this subject.

For example, say I have two products, a bucket and a spade, both in two sizes, small and medium, and both in two colors, red and blue.

I want to add a third size, large. When I add the large variants to the bulk exported CSV, before I import it back into the site, should I;

1. Clear the existing entries in the Variable ID field but leave the Variant ID column as empty with the header intact?

2. Remove the entire Variant ID column?

3. Simply leave the existing entries with the Variable ID entries for the new variants blank?

The support page: https://support.squarespace.com/hc/en-us/articles/360000694948-Exporting-products-to-a-csv?_ga=2.120737857.897915261.1589568602-1625168701.1580288092#toc-re-importing-your-products

Importing the .csv will create new products on a new page, rather than updating existing products across many pages. 

If you're importing products to a different site, remove the values under Product ID and Variant ID, leaving the headers intact.

This isn't clear to me, I don't want new pages, simply the new option in the page pull down.

Thanks,

Garry