We always recommend using our Inventory Protection feature to ensure your listing is protected when setting up promotions in Jungle Scout. However, you could also consider setting a "Max Order Quantity" directly from within your Seller Central account.
To set this up just go to your listing in Seller Central click Edit and go to the Offer tab (make sure the Advanced View option is enabled):
Scroll down to the Max Order Quantity option. Here, you'll have the ability to select the max number of products that a buyer can purchase per order (we recommend setting that to 1 or 2 units for the duration of the promotion):
Scroll down to the bottom of the screen and click the Save and finish button to save your changes
Remember, this will be the number of units a buyer will be able to purchase per order. If you set the Max Order Quantity to1 that means that buyers will only be able to buy 1 unit in a single transaction. If they want to buy more than that, they'd have to place another order.
The max quantity can be edited or disabled at any time and we recommend removing it after the promotion is over.