The compensation of all employees in the classified service of the state shall be uniform for positions within the same service, group, and grade as established by the classifications of said service as at any time made by the rules of the director of administrative services, provided a rate of compensation for such service, group, and grade has been fixed by the general assembly, except that the compensation of persons employed in the classified service of the state at the time of the fixing of a rate of compensation for the service, group, and grade by the general assembly which may exceed the uniform rate so fixed, shall not be affected by this section.