Distance Based Shipping Integration Index
Setting Units of Distance
Hold-outs to Napoleonic measurement are coloured grey. The rest of us use a sensible measurement system.
Your store will allow you to use the archaic units of imperial Britain. You set the units that Google will return in an option in the WSM->Shipping & Settings->Shipping Settings. This option is called Set Distance Based Shipping Method Units.
Your choices are imperial (miles) or metric (kilometers).