Err...For elder, it uses a different bonus. It has AddRace2 on it, which allows you to increase damage to predetermined mob groups defined in a DB file.
And for the record, AddRace and AddRace2 are counted separately in the source, which makes them different modifiers and thus they multiply with each other.
Turtle General on ratemyserver
bonus2 bAddRace,RC_NonBoss,20; bonus2 bAddRace,RC_Boss,20; bonus2
bAddRace2,5,20; bonus3 bAutoSpell,"SM_MAGNUM",10,30;
Elder on ratemyserver
bonus2 bAddRace2,5,40;
They say they boost damage on the fifth monsters type under bAddRace2 with elder boosting it by 40% and TG boosting it by 20%.