On grammatical class:

ce'i
digit/number: % percentage symbol, hundredths.
fi'u
digit/number: fraction slash; default "/n" => 1/n, "n/" => n/1, or "/" alone => golden ratio.
ki'o
digit/number: number comma; thousands.
ma'u
digit/number: plus sign; positive number; default any positive.
me'i
digit/number: less than.
ni'u
digit/number: minus sign; negative number); default any negative.
pi
digit/number: radix (number base) point; default decimal.
pi'e
digit/number:separates digits for base >16, not current standard, or variable (e.g. time, date).
ra'e
digit/number: repeating digits (of a decimal) follow.
za'u
digit/number: greater than.