Literal translation
to do master Arnaud's accounts
Meaning
to make muddled, misleading calculations
Explanation
The phrase plays on the homophony of conte, tale, and compte, account. Mèste Arnaud is a fictional figure standing in for the old-time apothecary, whose bad reputation was well known: French has faire des comptes d'apothicaire, and a Provençal saying warns against an apothecary's mix-up and a notary's endless fine print. To faire de conte de Mèste Arnaud is thus to make tangled, deceptive calculations, and by extension to tell a convoluted, twisted story. Apothecaries, both pharmacists and grocers, were wealthy merchants who handled large sums, hence their reputation for padded, drawn-out bills.