Headword and gloss are different forms of the same verbal form; cf. eta 80, eta 82.
The headword verb is a poorly attested form (in literature only in Lucian) of the second person singular, pluperfect, of oi)=da 'I know'; and according to Herodian, *peri\ o)rqografi/as 3.2.517, this form, and the more common one, h)/|dhsqa, derive from h)/|deis (= the present gloss) by e)pe/ktasis ('extension') of the qa syllable. According to Smyth, §798, this form occurs in the best manuscripts of Plato and elsewhere, but is less correct Attic [sc. than h)/|dhsqa] (web address 1).
The Lexicon Ambrosianum (Ambrosianus B12 sup. fol. 77r) has a similar entry to this one, but with better spelling: h)/|dhsqa: h)/|deis: kata\ e)pe/ktasin th=s *qa.
With the same headword as in the Lexicon Ambrosianum, glossed by h)/|deis (as here), note Hesychius eta120, probably interpolated -– according to Latte -- by the family S or N of Glossarium Cyrilli. However, the Glossarium Cyrilli, Coislinianus 394 fol. 113r has an entry identical to this one.