Doca Flow Action Descriptions

Context: When modifying packets using actions in Doca Flow, one can use Actions or Action Descriptions. Action descriptions have the benefit of being dynamic rather than decided at compile time, using strings “outer.ipv4.dst_ip” instead of struct accesses. For this reason, I am trying to use Action Descriptions to add a predefined number to a packet field.

In this table summary, what does “val” represent?
Is it even possible to use action descriptions to add a number to a field rather than add two fields together?