The only option is using the real stock.
Shopify has delisted the app and demanded that we remove the random stock and custom stock options from the app. We can only offer showing real stock values at the moment and it will render if you are indeed tracking stock.

In this case, it's a result of your total setting.

Follow these steps:

(1) Add the total to be the current stock level + 1 of your most in stock product

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(2) If you used the "hide on large stock" option - make sure you're not trying to test a product with more stock than your setting.

Have you verified (1)+(2) and saved your changes?

In this case, your app is not setup properly.

Follow the placement guide to add it to your store.