syncing to website

hello, the stock levels for a product on my website are correct in the stock manager but are wrong on the website.

https://www.ollyskins.com/product/ollyskins-2640-fluo-safety-pvc-chest-waders/

I have checked on other items too and it seems to pick up one number for all sizes.

Any ideas?

Regards
Rick

https://www.ads-software.com/plugins/woocommerce-stock-manager/