I suspect that if we're willing to say human minds are Turing Complete[1], then we should also be willing to say that an ant's mind is Turing Complete. So when imagining a human with a lot of patience and a very large notebook interacting with a billion year old alien, consider an ant with a lot of patience and a very large surface area to record ant-pheromones upon, interacting with a human. Consider how likely it is that human would be interested in telling the ant things it didn't yet know. Consider what topics the human would focus on telling the ant, and whether it might decide to hold back on some topics because it figures the ant isn't ready to understand those concepts yet. Consider whether it's more important for the patience to lie within the ant or within the human.

1: I generally consider human minds to NOT be Turing Complete, because Turing Machines have infinite memory (via their infinite tape), whereas human minds have finite memory (being composed of a finite amount of matter). I guess Egan is working around this via the "very large notebook", which is why I'll let this particular nitpick slide for now.