After changing the score field in the category registration screen and saving it, the new value is not registered.

1. Access the Catalog module;
2. Browse to Product Registration > Categories;
3. Select a category;
4. Click the actions button > Change;
5. Enter a value in the score field;
6. Save.

As a workaround and use of ordering score through the score field, it's recommended that the score be set up in the product registration. For more details: How does the Score field work?.