Hi Stratfordgc
Yes, you can do this. ATUM allows to set an out stock threshold value for each product, unlike Woocommerce that just allows you to put a single value for all the products. To set an out stock threshold value for each product you just have to get into the product page, and in 'Inventory' tab set the value you wish in the Out of Stock Threshold field.
Notice that to display this feature you have to enable it in ATUM general settings.
Hope this helps,
Best Regards,
Andrea.