τὴν μὲν τῶν ἐπιστολῶν ἐγὼ ἒγραψα, τὴν δὲ οὒ

I got only the following translation:

“I wrote one of the letters, but…”

I don’t understand “τὴν δὲ οὒ”,

could someone help? Much appreciated.

Out of context, but . . .

τὴν μὲν τῶν ἐπιστολῶν ἐγὼ ἒγραψα, τὴν δὲ οὒ[κ ἒγραψα]

(It should be elided: τὴν μὲν τῶν ἐπιστολῶν ἐγὼ ἒγραψα, τὴν δ’οὒ . . .)

τὴν μὲν … τὴν δὲ means “the one…the other”