If you made changes during this year’s Summer Benefits Open Enrollment, they became effective September 1. However, your paycheck won’t reflect those changes until October. 
Premiums costs and Summer Benefits Enrollment elections may cause slight changes in your paycheck. Compare your October check to your benefits elections to ensure the new deductions reflect what you selected.

To view your benefits elections, log in to ERS OnLine. If you have further questions about payroll deductions, contact ESO at ext. 8060.

Source: ERS