If every color is available in all the sizes, this product will have 16 variants. There are four sizes and four color options so a total of 16 different choices, or variants. When you apply a quantity break price to this product it will create a duplicate hidden variant for each of those options, so you would then have 32 variants. If you added another you'd have 48, and another 64, and so on.
Shopify only allows 100 variants per product; sometimes this becomes an issue when Quantity Breaks is trying to create the price tiers and runs out of variants available. If this happens, the app will skip the product when trying to create them and send you an email notification listing the product that was the issue. Also, keep in mind your Shopify plan has a limited number of variants as well depending on what plan you are on. So even if you don't max out the product's variants, you might max out your overall variants. To fix that you need to upgrade your Shopify plan to one that allows more variants.
We created an app called Product Options which allows you to create an unlimited number of options for products and they don't count as variants. If you need to have many different options and quantity breaks, we recommend using Options to handle the options for your products.
The Quantity Breaks (standalone) app is no longer available for new installations. If you are currently using Quantity Breaks (standalone), you will be able to continue using the app on a grandfathered plan.
Any new installs of the Quantity Break app will be redirected to Custom Pricing which has a Quantity Breaks plan available. For more information on Custom Pricing, please visit Custom Pricing: Information and Overview.