I honestly can't imagine this concretely at all.

Tell me to imagine a spinning cow. My experience is a lot like evaluating the mental version of:

  class Cow:
      spinning = True

OK, so I don't know if other people actually visualize arithmetic or not. I don't think so, but I also wouldn't think that people literally imagined an apple, either, and yet here we are. But let's assume that people don't usually literally imagine pictures of the numbers in their mind when they add them.

Take 12. Add 7 do it. Now you have 19, right?

My mental imagery of adding 12 + 7 = 19 is nearly identical to that of picturing a spinning cow. Take a cow. Spin it. Now you have a spinning cow, right?

In both cases, those are just facts. Now, higher math does look like something to me, as does writing code. Those do have geometric shapes for me, kinds of blobby things with curved edges but not colors, except maybe rainbowy shimmers on those curves. I can feel the shapes moving and bending, and that moving and bending makes them makes sense to me. "OK, so I'm trying to do a binary search of this set... Alright, so if I push this shape into there... Oh! That'd work! Alright." But in no case do those shape-like things resemble anything I've ever seen in the real world.