When the integration creates new products there are two visible fields we have access to. It uses the POS integration ID to populate the SKU field in Shopify. It populates the Barcode field in Shopify with the UPC received from the POS.
We also create some metafields when we create the product. The metafield namespace for these is MRproductInfo
On the product level, we create a metafield with the key name "ALU" which should contain the RunIt style number, possibly appended to the Brand name (Runit does not enforce uniqueness of the style, except within a brand)
On the variation level, each item has a metafield named ALU, which contains the parent style number plus the options (if any)
Shopify does not expose metafields in the standard interface, but there are plug-ins that can be added to allow you to see them. Do a search on metafields in the app store to try some of these out. They should allow you to view and use the hidden metafields.