The sumti which refer to numbers consist of the cmavo li (of selma'o LI) followed by an arbitrary Lojban mekso, or mathematical expression. This can be anything from a simple number up to the most complicated combination of numbers, variables, operators, and so on. Much more information on numbers is given in Chapter 18. Here are a few examples of increasing complexity:
li  .abu  bi'epi'i  xy.  bi'ete'a  re  su'i  by.  bi'epi'i  xy.  su'i  cy.  
thenumber  a  times  x  topower  2  plus  b  times  x  plus  c  
ax^{2} + bx + c

An alternative to li is me'o, also of selma'o LI. Number expressions beginning with me'o refer to the actual expression, rather than its value. Thus Example 6.95 and Example 6.96 above have the same meaning, the number four, whereas
and
refer to different pieces of text.
The implicit quantifier for numbers and mathematical expressions is su'o, because these sumti are analogous to lo descriptions: they refer to things which actually are numbers or pieces of text. In the case of numbers (with li), this is a distinction without a difference, as there is only one number which is 4; but there are many texts “4”, as many as there are documents in which that numeral appears.