A 457 plan on ESS

We would like for our employees to be able to enroll, stop or update their 457 benefit via ESS. However, upon setting it up and doing some initial testing, it only partially works. If the employee is stopping the benefit or using a percentage, it works. If the employee puts in an annual amount, it is annualizing the amount again. Does anyone use ESS for 457? If so, can you share your setup with me?

Thanks in advance