MAI (http://www.lojban.org/en/publications/reference_grammar/chapter18.html, http://www.lojban.org/en/publications/reference_grammar/chapter19.html)

When suffixed to a number or string of letter words, produces a free modifier
which serves as an index number within a text.

pamai mi pu klama le zarci 1-thly, I [past] go to-the market. First, I went to
the market.

