This is interesting. Here are some thoughts.

Changing the digits via poses files that sets the values of the shaderNodeParm channels controlling Ambient_Value, should work, but the change might not show up in preview.

I guess changing the digits via a dial, where the dial value equals the displayed digit, would be the best way from the stand point of an end user, but setting up ERC to implement that for Ambient_Value sounds like a gargantuan task.

I think the easiest way to change the number via one dial would be to use geom switching. Unfortunately that requires using ten different obj files. The idea is that each obj has a material zone in the shape of one specific digit. Attached is my attempt to implement that.