This is from Appolodorus 3.6.7. It does not refer to specific parts or phases of intercourse. You should read the numbers as percentages, as the translation indicates:
Hence, when Hera and Zeus disputed whether the pleasures of love are
felt more by women or by men, they referred to him for a decision. He
said that if the pleasures of love be reckoned at ten, men enjoy one
and women nine. Wherefore Hera blinded him, but Zeus bestowed on him
the art of soothsaying. The saying of Tiresias to Zeus and Hera: "Of
ten parts a man enjoys one only; but a woman enjoys the full ten parts
in her heart."
In the original text, the saying reads:
τὸ ὑπὸ Τειρεσίου λεχθὲν πρὸς Δία καὶ Ἥραν·
οἴην μὲν μοῖραν δέκα μοιρῶν τέρπεται ἀνήρ,
τὰς δὲ δέκ' ἐμπίπλησι γυνὴ τέρπουσα νόημα.