I was reading the Qiskit tutorial on circuit properties and there is a section (Unitary Factors) which states that even though an example circuit is made of 12 qubits, it may not need 12 qubits to run.
The original circuit: here
The layers of the circuit: here
It is stated that: We can see that at the end of the computation there are three independent sets of qubits. Thus, our 12 qubit computation is actual two two qubit calculations and a single eight qubit computation.
I am struggling to understand where in this diagram it is illustrating that we only need two 2 qubit calculations and one 8 qubit calculation.