A counting number (5)
(Other definitions for eight that I've seen before include "VIII" , "Set of rowers" , "Figure" , "destroyed [IN 8A] here!" , "A number, sounds like swallowed" .)
(Other definitions for three that I've seen before include "trilogy" , "So many 12s today" , "Feet in 3 Down" , "There (anag.)" , "Start to count back, briefly" .)
(Other definitions for eighteen that I've seen before include "Treble six" , "majority number" , "Number of on-field players in an Australian Rules football team" , "XVIII" , "Old enough to vote" .)
(Other definitions for nine that I've seen before include "Number of Muses and days in a Novena" , "So many" , "Number for a club" , "A perfect square" , "Number of the ancient Muses" .)