libphonenumber/resources/metadata/36/altformats.csv

1	Format	Parent Format	Comment
2	X XXXX XXX	fixed_1/3/4	Local numbers are also often written 4-3 rather than 3-4.
3	XX XXXX XXX	fmt_2/3/3-4	Local numbers are also often written 4-3 rather than 3-4.