"Low sales numbers" refers to a situation where a product or service is not being purchased by many people or customers. It means that the sales or the amount of items being sold is relatively small or not meeting expectations. Full definition
If there's an explanation for a particularly low sales number, you can include it. (smithpublicity.com)
If you've avoided it, you're not alone; low sales numbers show that the franchise is growing stale. (themarysue.com)
On the other hand, there aren't any other good cars with low sales numbers in the Pope's U.S. driving fleet, so the 500L does have that blessed benefit. (autobytel.com)