Leave reduced price option empty if you don't want to offer reduce price.
If this value is provided products will have this reduced price displayed as shown below.
Walmart.com list of products page:
This is how it will look on Walmart.com product details page (buy box):
Please note also that Walmart expects products to be submitted first without a reduced price, and after a product is published, a seller can submit a reduced price. This means, if you submit a products to Walmart for the first time (it is in draft and you try to make it live), and this product has a reduced priced specified, you may need to resubmit the reduced price again after the product is live if a reduced price did not go through with the initial submission of the product..
Please follow the steps:
1. Export to Walmart your draft products with only regular price, keep reduced price empty. See this post how to export products to Walmart.
2. When you are sure your products went through successfully and Walmart has it in its database, you can add reduced price value for your products and submit.