What is this $10 late-renewal fee?
Most top-level domains (TLDs) have a grace renewal period. This period is typically up to 40 days and it allows the registrant the chance to renew their domain even after it has expired. During the last 10 days of this renewal grace period, Dynadot charges a $10 late-renewal fee.
For example, if you own a .COM domain that expired on January 1, 2017, you would have been able to renew your domain at the regular renewal price until January 30, 2017. After this date and until the domain was deleted on February 9, 2017, you would have been charged a $10 late-renewal fee, so your total renewal cost would be $18.99 ($10 fee + $8.99 regular renewal price).
Following the TLD's grace renewal period, your domain is deleted and put in redemption. During this period, you may still be able to restore your domain, but at a much higher price.
NOTE: Please keep in mind the renewal grace period is time stamped, meaning if the domain was registered at 11am PST, it will also expire at 11am PST on its expiration date. This means the renewal grace period will end at 11am PST as well.