TIER n.
A row or rank, especially one of two or more rows placed one above, or higher than, another; as, a tier of seats in a theater. Tiers of a cable, the ranges of fakes, or windings, of a cable, laid one within another when coiled.
UNDER prep. 2 definitions
Denoting relation to something that exceeds in rank or degree, in number, size, weight, age, or the like; in a relation of the less to the greater, of inferiority, or of falling short. Three sons he dying left under age. Spenser. Medicines take effect sometimes under, and sometimes above, the natural proportion of thei…