It means 2 less than failure, or 1 less than failure.
I don’t know how many reps you can do, I don’t know your max effort. So we say -2x to imply stop 2 reps short of your failure.
That way you focus on good form, rather than simply doing as many reps as possible with potentially bad form.
You may also see “form failure”, meaning do as many reps as you can with perfect form