In the US, distribution voltage is usually 480V. However, most industrial equipment is only rated for 460V. Why is this the case?
The feeder wires that deliver power have a small resistance/reactance. When a current flows through them a percentage of the source voltage is lost to the wires. So the voltage at load will be less. 120V at panel, but 115V at loads. If the voltage is higher than 115V, it is just better efficiency.
Electric codes set maximum loss to feeders. It's how we size wires for installations.
In your case, 480V at source, 460V required by load (nominal ratings) and a maximum of 20V lost to the wires.
It's just Ohm's law applied to a series circuit with a small resistance (wires) and a large resistance (load).
This is exactly the same situation as regular 120 Vac Mains voltage. Although North American AC Mains voltage is often called 110 Vac or 115 Vac or even 117 Vac, the actual voltage as specified by the power utility is 120 Vac.
That's because the power utility tries really hard not to exceed 120 Vac at your power outlets. Doing so causes incandescent lamps to burn out faster and causes resistive loads to consume more current than they would at a lower voltage such as 115 Vac.
The 480 Vac Mains is treated exactly the same way. Maximum voltage is supposed to be 480 Vac but nominal voltage is set to 460 Vac.