The term "existing" in the mind kind of covers up a lot of details. You can actually estimate the bounds of everything that can possibly exist within someones mind.

It's similar to thinking about what are all the possible things that can exist in computer memory? It's basically the total permutations of 1s and 0s.

The same thing goes on with the human brain, only the primitives are not 1 and 0. The primitives are much more complex but they are finite. One turing-complete-esque model for the human brain is the ML neuron with weights. It may be possible to model the entire human brain as just a composition of all these primitives. If not, then maybe some additional primitives to complicate things may work as well. The key here is to realize that it's more complex than binary memory but like binary memory the amount of things that can "exist" in a human brain is finite and countable.

So it's a combinatorics permutation problem of the state of all primitives in the brain.

When you bring the concept closer to actual formalization by technically modelling what the brain is, the rest of the philosophical question requires formalization as well.

Clearly when something "real" exists in your mind it is data compression. A fewer number of primitives is symbolically representing an actual thing that exists. What are all the possible things that can actually exists?

Well that's another combinatorics problem. Take all fundamental particles and compose them in all the ways possible and that's your total.

So essentially it's using high level primitives in memory to symbolically compress data in the real universe represented as atomic particle primitives.

Once all the details are in a way formalized and actualized in your brain you can easily disprove this "argument". Right? It's simply large compositions of primitives (atoms) being represented by a smaller amount of primitives (neurons) in the exact SAME way a computer represents say a world in an open world game. The whole thing is a linguistic trick. You need to visualize this problem as a physical actualization: Data and atoms (the data is the state of neurons in a neural net but in the end that's just made up of atoms too so it's technically atoms representing atoms).

This helps you get past all the bullshit word play in the original question. Not all chunks of data in a computer/brain represents compressed data from something that actually exists. It's all a matter of interpretation too. I can have a single bit represent the entire concept of god if I wanted to.

Anyway this isn't even a refutation of the argument. It's just a detailed description showing that people aren't even sure about what they should be asking here.

Is a certain stream of data in the brain a compressed version of an actual combination of atoms that exists? Or maybe is it a compressed version of something that isn't atoms but "god" or some other bs? Well the point of my whole argument was that what the "data" represents here is irrelevant. I can interpret 1010101010101 to mean understanding of god, you can interpret it to mean your sock drawer. How can someones interpretation of something influence whether or not it's compressed data of something that actually exists? No. It's not, it's like asking a someone the color of music... completely irrelevant, like Anslems entire argument... not even asking the right question.