Amazon PPC glossary
Buy Box percentage
Buy Box percentage is how often your listing holds the Buy Box, the main Add to Cart button. If you do not hold it, shoppers who click your ad may not be able to buy from you directly, so your ad spend can be wasted.
Example
Your listing holds the Buy Box 95% of the time. For the other 5%, another seller’s offer is shown, and clicks from your ads during that time are far less likely to turn into your sales.