Your calculator has flat batteries maybe smile
Im getting 4 on both my casios (fx602p, fx82super)
What did you type?
[2] [+/-] [X²] result 4
[2] [X²] [+/-] result -4

Any negitive number squared makes a positive number and -2 is a negitive number last time i checked (which was a while ago so maybe they changed the rules of math lately?)