B.A.P release more teaser posters for comeback

Zelo, Youngjae, and Himchan have followed in Bang Yong Guk and Jongup's footsteps to individually release a teaser poster each via Twitter for B.A.P's long-awaited comeback.  The only one to not do so yet is Daehyun.

The same 'Matoki' characters in different poses appear, looking angry, clownish, and curious in each with the letters "R", "X", and "T" above.  Previously, the numbers "A" and "I" were found on the teaser images.  What might this signify?