Lena is giving Aisilian her very sharpest icy 'we will talk about this later' look, with a side of 'this is not a joking matter' (Idania is also getting a tiny bit of this, but it is mostly directed at Aisilian). At this, however, she clears her throat and explains backups, with brief diversions into forks and cortical stacks as a subset of backups.