Right-Facing Arrow Above an Expression in Mathcad Prime 10

Hey everyone,
I've been working with Mathcad Prime 10 for a couple of months now, and I recently came across something that has me stuck. I’ve tried searching for a solution in multiple ways but haven’t been able to figure it out.
In the equation I’m working with (in reference to the attached image), there is a right-facing arrow above the expression: concat( num2str( d/mm ), "mm" )
I’d like to understand what this operator is called, it`s function, and how to insert it in Mathcad Prime 10. Any insights or guidance would be greatly appreciated!
— Srikar

