A330 apu master switch "on/r" definition?

[Beechcraft Driver]

Quick question regarding the apu control on the a330.

The apu master switch in the flight deck has the blue light "on/r".
I can't seem to find anywhere what the "r" stands for.
Can anyone help me out?

Thanks!!!

[KingAir1978]

The 'R' is there because it is possible to R eset the electronic control box. Have a look in your QRH, abnormal procedures, resets.

[fantom]

Look above your head. It says 'reset'.