Garnishments - changing the rule ID changes the deduction limited by proration

I have an employee with two separate child support garnishments. If I change the Rule ID for the first one to the 12 weeks' delinquent, the proration for each of the two amounts changes? The proration rule ID is the same for both. I was expecting the Rule ID to change only the maximum allowed deduction.

If both garnishments are set to the standard 50%:

The max deduction is 463.77, amount 1 is 656.50 and amount 2 is 386.

I see the amount 1 on the check as 292.05 ⇒ (656.50 /(656.50 + 386)) * 463.77

I see the amount 2 on the check as 171.72 ⇒ (386 /(656.50 + 386)) * 463.77

When I change the first garnishment to the 12 weeks' delinquent rule ID, my maximum deduction amount changes to 510.15