Issue in /src/pages/rest/tutorials/configurable-product/define-config-product-options.md

In the `Set the configurable attribute` section, it's unclear where we should get the value for `value_index` from. All the tutorial says is that `The value assigned to the value_index must be unique within the system.` So what should we put there? Any random number will do?

Open src/pages/rest/tutorials/configurable-product/define-config-product-options.md and read the “Set the configurable attribute” section. Trace the documented value_index field to the surrounding API guidance or referenced Adobe Commerce model, then update the explanation so readers know where the value comes from and how to choose it.

Written by the indexing model from the issue text.