[Asiaplay]

am2003,

The quantity in stock for each "Variant" is stored for each combination (so yes, this can be tracked and updated for each combination / variant).

If you open a product for which you have ALREADY set up variants for you will see in the header choices "Product Variants" - click on that and you will be able to change the stock level for each product variant (each combination).
Basically the "Product Variants" option appears as soon as you have added "Product Options" for a product - so is two step process for each product (set up Product Options, then open Product Variants to change stock level and if wanted allocated product photo for each variant / combination).

By default X-Cart adds a number to the end of your SKU when you add variants
e.g. Original SKU for product is SS1234 (you can manually edit these to use the SKU number you want for each variant - but there can not be duplicates).
SS1234-1 Black - XS
SS1234-2 Black - S
SS1234-3 Black - M
SS1234-4 Black - L
SS1234-5 Black - XL
SS1234-6 White - XS
SS1234-7 White - S

So clarifying for a product with variants - the STOCK level is updated in the "Product Variants" area and not in "products" where a stock level is normally undated if the product does not have variants - there is a warning which shows up for the stock level when you open a product actually (so you will see this).

Note that you can also import these via CSV "Product_Variants" - see import / export CSV manual if you ever choose to do that (is pdf manual which can be found by searching for "import export guide" here in the forums).
Easiest way is to set up one product manually and then do an export of your "Products" and also "Product Options" and "Product Variants" in X-Cart Admin. (best to do these as 3 separate exports - as it is much faster and easier to import as 3 separate imports if you choose to do that later).

Hope additional comments make this clearer for you - cheers, Asiaplay

PS: you can also have a different photo for each variant - so when a person changes from white to say red - then they get to see the red product photo.