en_tn_condensed/jdg/09/20.md

But if not

The rest of this phrase can be understood from what Jotham said in verse 19. Alternate translation: "But if you did not act with honesty and integrity with Jerub Baal and his house" (See: rc://en/ta/man/translate/figs-ellipsis)

let fire come out from Abimelech and burn up the men of Shechem

Jotham is speaking a curse. He speaks of Abimelech destroying the people of Shechem as if he would burn them with fire. (See: rc://en/ta/man/translate/figs-metaphor)

Let fire come out from the men of Shechem and Beth Millo, to burn up Abimelech

Jotham is speaking a curse. He speaks of the people of Shechem and Beth Millo destroying Abimelech as if they would burn him with fire. (See: rc://en/ta/man/translate/figs-metaphor)

Beth Millo

This is the name of a place. See how you translated this in Judges 9:6.