digit/number: arbitrarily small/lesser/diminished/few (finite and nonzero but otherwise as small as desired).
No assumption about signum; the above definition is given in absolute value terms. In other words, the typical meaning of "arbitrarily and positively small" is "ma'umei'a", meanwhile "arbitarily small in absolute value but negative" is given by "ni'umei'a". See also: zau'u.