Exegesis:

aitēsas pinakidion ‘having asked for a writing tablet,’ by signs of course.

aiteō ‘to ask,’ ‘to ask for.’

pinakidion ‘writing-tablet,’ consisting of a small board (yew tree, according to Jewish sources) covered with wax.

egrapsen legōn lit. ‘he wrote saying…,’ but legōn is a literal translation of Hebrew leʾmor which can introduce indirect speech even when the words are not spoken but written, cf. 2 Kings 10.6.

Translation:

Asked for. In some languages the corresponding verb can only be used when speech is implied; hence e.g. ‘he caused to be brought’ (Kannada).

Writing tablet, or somewhat more generically, ‘board/thing-to-write-on’ (Sundanese, Batak Toba), ‘that on which he could write’ (Tboli); or, ‘slate’ (Balinese, Marathi; also Tae,’ Kituba, lit. ‘stone on which-to-write’).

He wrote, usually to be followed by a marker of quotation, e.g. ‘thus’ (Tae’). In some cases a marker which primarily refers to quoted speech can also be used with extended meaning in reference to writing, e.g. ‘its-sound’ (Malay), ‘saying’ (Sranan Tongo, Navajo, Apache).

And they all marvelled, or, specifying the connexion with what precedes, ‘therefore they all were perplexed’ (Batak Toba), ‘they all were astonished at it’ (Bible de Jérusalem), ‘that surprised them’ (cf. Phillips). For to marvel see on “wondered” in v. 21.

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.