indicative vs subjunctive in terms of conveying meaning

In A Comprehensive Grammar of the English Language (page 156), the book gives these examples for WERE-SUBJUNCTIVE (for showing the structural differences between indicative vs subjunctive constructions):

Later the book describes the were-subjunctive as:

The were-subjunctive (or past subjunctive) is hypothetical or unreal in meaning.

As I said, I know the structural properties of subjunctive constructions but I wonder what a native speaker of English language grasps/understands when hearing/reading those above mentioned examples (in terms of meaning)