How to get Civil Labeler elevation to stay on a set terrain (instead of active terrain)?

ORD 2021 R1 (10.10.01.03)

Hello,

For the civil labeling, I want the elevation text in the tag to be shown from a specific terrain. Right now, it is just set to whatever terrain is active at the moment, so it switches from one to the other. How do I set this to just go off of one of them?

Thanks!

Ben