36V bikes with 250W motors are rarely fitted with controllers that can take 60V batteries. That little blurb is talking about something else,. It could be the display, if you have one.
A true 6)V battery goes up to 67.2 volts at max charge, Here's the max voltages
42.0V for a 36V battery
54.6V for 48V
58.6V for 52V
67.2V for 60V