The imperfect of ἀντιβολεω

Greek Learning Greek
1

In Lysias 1.25 I came across the imperfect of ἀντιβολεω: ἠντεβόλει. My question is, why does there seem to be two augments, the η and the ε? eg why isn’t it like ἀντεβολει or ἠντιβολει?

2

Smyth 451:

Double Augment.—Some verbs take two augments, one before and the other after the preposition, as ἠν-ειχόμην, ἠν-εσχόμην from ἀν-έχομαι endure, ἠν-ώχλουν from ἐνοχλέω annoy, ἐπηνώρθωμαι from ἐπανορθόω set upright. So also, by analogy to the foregoing, a few verbs derived from compound words: ἠμφεσβήτουν from ἀηφισβητέω dispute, ἠντεδέκει from ἀντιδικέω go to law (ἀντίδικος).

http://www.perseus.tufts.edu/hopper/text?doc=Smyth+grammar+451&fromdoc=Perseus%3Atext%3A1999.04.0007

3

Thanks again!