When using a single number, it is interpreted as a percentage:
L.pie([50.66, -0.0], 45).addTo(map);
You can also pass an array of {num: Number, label: String}-maps:
L.pie([50.68, 0.05], [
{num: 45, label: 'Bob'},
{num: 60, label: 'Tom'},
{num: 45, label: 'Ada'}
]).addTo(map);