In chapter 57, he has 60 days left. He gets locked up in Chapter 59, and Astria is anxious about doing so but says he will be held until tomorrow. In chapter 60, we get a two-in-one, Sena's maid saying her majesty will be visiting today and Sena's jailer asking him to stop trying to escape as he hasn't slept in two days, this is Sena's 10th escape attempt, and Astria knows this isn't the first try when visiting. In chapter 61, it is early dawn and he has 59 days left, with the cliffhanger last chapter happening at least 5 hours ago after eating. Either an eventful day, or poor storytelling.

In chapter 63, Astria kisses Sena to share a cure all potion. This takes place the same day as 61, so he still has 59 days left. Chapter 64 opens with Sena feeling better physically, but his lifespan specifically is still the same and he remarks Astria isn't bothered by yesterday's kiss. At this point, he has 59 days left. Chapter 65 opens with him have 68 days left the next day.

This becomes even stranger as after Astria learns about how babies are actually made, there is a lot more kissing and attempted interc**rse which leads to a question: Is the author trying to create an image of two (shorter) adults getting intimate, or an adult and a child doing it? Needless to say, this isn't a question that should need to be asked about the main pairing in a romance novel.

Sena and Astria's relationship. This is more nitpicky, but the author can't decide what Sena feels for Astria. He repeatedly states Astria is unforgivable, he hates her, etc but has unrecognized romantic feelings for her. It doesn't feel like a tsundere thing either, as his distaste is stated after she treatens war, "babymaking", the livelihoods of others for his affection or just killing them for bumping into him. Very legitimate reasons to not like someone, and it's meant to be taken seriously but gets forgotten 2 chapters later.

Also, it's heavily implied in Chapter 61 that Astria gave him a hickey, yet when it happens again in Chapter 73, it's somehow the first time. So my faith in the continuity is shrinking. Nitpicky, even for this section, ik.

a bland adventure novel with two not-lovers, Sena and Astria, with a random numbers pretending to be Sena's lifespan.

This doesn't mean their relationship advanced naturally. What happened was Sena decided being forcibly kissed and almost SA'ed was enough to debate his feelings for Astria.

This, along with the author cutting 25 days from Sena's life (52 -> 27), makes it feel rushed as if they didn't know what to do with the plot. Sena decides to return to his hometown, but Astria comes along with him without complaint.

Sena himself mentions he will need the full month to make it, and with her, he very likely won't. Yet he does it because he wants to show Astria the world outside despite knowing how little time he has.