Grade Rate Value HSDL Error

Summary:

I am loading the same grade rate values into two non-prod environments and getting an error. The only difference is the effective start date.

Content (required):

In environment A I used a PAST effective start date. In environment B I used a FUTURE effective start date and that's where I'm getting the error below:

The line for component GradeRateValue with instruction MERGE doesn't include values that define a unique reference to the record. Include values for at least one of the supported keys.

I've looked at the support article Doc ID 2507825.1, and I've reviewed the business object, but it's not clear how the information there should change the Key, since in the HSDL it's populated automatically.