Physical numeric keypads in a rectangular grid give the 5 key a tactile mark distinguishing it from the rest (ITU-T E.161 has the details). India adds that soft-key keypads on public terminals such as fuel pumps and point-of-sale devices should offer another way to locate and navigate keys, such as audio through a private headset.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.