It means the following;
2 – Slot number. This is a holdover from the CMS, there really are no slots in the AX, so just ignore this.
0 – again a holdover from the CMS. Ignore this.
2 – Interface type. 1 = FXS, 2 = FXO
2 – Line/port number.
So in this case the call used line 2 of the FXO.