x1 is a mass formed from a set x2 of n members, one or more of which is/are x3, [measured relative to the set x4/by standard x4]

x1 is the (n)th member of set x2 when ordered by rule x3 [by standard x4]

x1 is an (n)th portion of mass x2 [by standard x3]

event x1 has probability (n) of occurring under conditions x2 [by standard x3]; the rafsi is borrowed from cunso ; see Section 18.20

x1 is at scale position (n) on the scale x2 [by standard x3]