Jeppesen route MEA suffix "a"

[Dupre]

Hi, apologies if this is not the correct forum... mods please move if there is a more appropriate place.

In the Jepp Enrote charts, the MEA sometimes has a suffix... I have found in the introduction section some definitions includint a "G" and "T" suffix. But cannot find the definition "a" suffix.

Can anyone tell me?

Thanks!