Why does ACA Plan Start Month change back to 01 after ACA_MERGE?

One of our companies has a Plan Start Month of 11. I added the Benefit Programs and Plan Start Month of 11 for each on the ACA Data Extract Definition page. When I ran the ACA_EXTRACT to Extract All Transmittal Data, the process correctly adds 11 as the Plan Start Month for all employees on the ACA Employee Transmittal Data page (ACA_EMPLOYEE).

I also load all monthly data and amounts for Box 14, 15, and 16 via Excel to CI, which populates the Review Employee Data Load and Review Employee Amount Load pages. However, when I then run the ACA_MERGE process to merge data, it replaces the 11 for all employees with a 01 on the ACA Employee Transmittal Data page. Has anyone else experienced this? Why is it overriding the Plan Start Month of 11? Is there something I'm missing?