In the PS1 core control settings menu, the face buttons are labeled "A", "B", "X", and "Y". However, the Playstation doesn't use letters for it's face buttons; it uses symbols. This makes it challenging to properly map controls.
The proper labels would be:
A -> O
B -> X
X -> △ (U+25B3 White Up-Pointing Triangle)
Y ->◻ (U+25FB White Medium Square) (This character is rendered incorrectly here; copy and paste it into notepad or the search bar to see what it actually looks like)