It's been stated in various online media presumably because Benfica have to release basic details.
The Times has it as:-
"Liverpool have agreed a deal with Benfica worth an initial £64 million for Darwin Núñez, the Portuguese club have confirmed. The striker, who will begin a medical on Monday, could eventually cost Liverpool £85 million.
Liverpool will pay €75 million (£64 million) for Núñez with a potential further £12.8 million linked to appearances and £8.5 million based on the forward performing in a successful team."
The Mirror has:-
"Portuguese paper Record, as cited by Sport Witness, claims that the agreement will see Benfica receive £64.2million (€75m) upfront from the Reds but that there are £21.5million (€25m) in easily attainable add-ons.
An extra £4.3million (€5m) will be paid after Nunez plays 10 games for his new club and when he hits the 60-game milestone, £8.6million (€10m) will be paid. The remaining £8.6million (€10m) will depend on performance-related objectives, both individual and collective. That takes the total value of the deal up to £85.5million (€100m).
These precise figures are contested by The Times, although there is consensus over the initial £64.2million agreement and £12.8million potentially linked to appearances and £8.5 million based on the forward performing in a successful team."
