By the statblock, right. The poster who mentioned the 20 glabrezu was making a point about monsters' non-stat advantages.dcollins said:A Balor's summoning ability is only usable once per day, summons a single glabrezu, and only lasts for an hour. Therefore having 20 glabrezu is outside the standard abilities of a balor.
Tuckerites say the kobolds are dangerous because of their traps and their environment, even though the statblock doesn't state that they are always encountered near traps. Similarly, a balor (as the general of a fiend army) might be encountered with few dozen glabrezu bodyguards, though that is not explicitly part of his stats, powers, or CR. The point is, in these situations neither the kobolds nor the balor is the major component of the EL.