When you put a valid PLC address in the PLCAddressText property, that value will be read from the PLC and displayed on the button. If you wanted to show different words, then your PLC would need to support strings. Any data type can be used for this.
Another option for switching text is to use PLCTextAlternate. If the value read from this is True, then the text put in the TextAlternate property will be displayed, otherwise the value in the Text property will display.