Box 10 is used for the value of employer-provided on-site day care. I've never before heard of a case where the employer was a day care itself, but it makes sense. If the day care provides free or discount care for its employees, the value of that has to be counted as an employer benefit in box 10, or it would have to be added to her taxable wages. The second employer may be in non-compliance.
Non-qualified amounts of dependent care benefits will be added back to your taxable income and taxed at whatever your marginal tax rate is, although there is no additional penalty.
