When you onboard your employees to payroll, we require their date of birth (DOB) and SSN to complete their profiles. When it's provided we send DOB/SSN directly to Check (our payroll partner) to complete the onboarding but we don't store a copy on our servers.
That's why, when you get back to employee profile in settings, you only see asterisks in place of DOB and SSN. This is done to visualize that this info was provided earlier, but we can't (and don't need to) retrieve it.
When editing employee profile, if you provide new values for DOB or SSN, it will overwrite the existing one.