What's convenient for him is to be somewhat rushed - he really does have a lot to do today! and tomorrow, and for the foreseeable future! - but not too preoccupied to be warm with her.
Over the meal he mostly talks about the situation in the south, at least the not-especially-sensitive elements of it. It's characteristic of him – he picks women who are clever and insightful, and then likes to think out loud with them – and pretty much anything related to his political work is going to be filling in useful context for Carissa, right now.
So he can pull out a map, and explain their current difficulty! They recently annexed a region called the Tozoa Plains (now Tozoa Province). It was an obvious choice; plenty of arable land, far enough south for a long growing season, previously limited by its dry inland climate and a lack of major bodies of water for irrigation but the Empire can easily build aqueduct infrastructure and canals over the next decade, at which point they expect high agricultural productivity. It had been inhabited by nomadic herding clans with no state-level structures to organize resistance; it was cheap to conquer.
They would like to move further south and annex the main body of Oris, the kingdom that on paper used to hold the Plains as an outlying province (but did not especially mount a resistance; they hadn't even been able to administer or collect taxes on the plainspeople, let alone farm the arid plains.)
The issue is that they're now stretching their non-Gate supply chains rather far, and the canals and canal-Gates won't be complete for a decade. The plains are separated from Tolmassar Province, the region directly north, by a mountain range. Marching on Oris overland, or supplying their army, can only be done via Widow's Pass, which is a difficult crossing;
The straight-line path from Jacona that would avoid inconvenient mountain ranges – the route along which they want to place a canal – would run through Taymyrr, which is (or recently was, rather) a well-defended kingdom, though not nearly as wealthy or organized as the Empire. They've now conquered about half of its total land area; they're now holding Stormhaven, the capital, and have the former king under compulsions. But they're running into substantial remaining resistance – both in the southern half, which consists of a looser patchwork of feudal holdings that shouldn't really be able to coordinate their forces nearly this effectively, and local resistance in the garrisoned region.
The resistance is ostensibly getting support from Zoskin, the small and very mountainous state directly south of its border, but Altarrin is suspicious that those resources actually come from the Empire of Holy Ithik – which, like Iftel, has a state religion, though not a magical barrier to go with it. The Holy Empire shares a border with Jacona province, and has historically been on rather tense diplomatic terms with the Eastern Empire, though there's never been a land war in either direction.
The military commander leading the invasion in Taymyrr, General Isktar, is competent, and has the important trait of maintaining strict troop discipline and tending to treat conquered peoples relatively well, which matters in this case because Taymyrr had a reasonably functional bureaucracy and infrastructure before this, and incorporating them will be cheaper for the Empire if they can work with the existing nobility rather than replacing them. There's no one Altarrin would rather have in charge. But, at the same time, Isktar is...maybe not paranoid enough to stay on top of an underground resistance.
(He doesn't outright say that the problem is that Isktar doesn't dislike the gods strongly enough, but it's there to be read between the lines.)