Generally speaking, a Net Promoter Score that is below 0 would be an indication that your business has a lot of issues to address.
A score between 0 and 30 is a good range to be in, however, there is still room for progress. If your NPS is higher than 30 that would indicate that your company is doing great and has far more happy customers than unhappy ones.
An NPS over 70 means your customers love you and your company is generating a lot of positive word-of-mouth from their referrals. The higher your NPS is, the more likely it is that your customer referrals will convert into new leads and more revenue for your company.
Do your best to keep your score above 0. Even though an NPS of -10 might be higher than others in your niche, finding yourself below zero might be discouraging and it should definitely ring a bell as to the provided customer experience.