Rules of exploration mode of Pathfinder 2e had recently puzzled me.

1. Here is said that every 24 hours characters need 8 hours of rest and if they'd go for more than 16 hours without it - they'd be fatigued.
2. Here is table of distances that characters can cover - and it's clear from that table is that per day characters are supposed to spend only 8 hours walking.

Is there any explanation about what happens during the other 8 hours before rest? Are there some mandatory activities that take those 8 hours? Is there limit on time of activity characters can do during day? Like - if characters spent 8 hours to reach some ruins - can they start exploring them? Because, according to rules of travel - they are too tired to walk anywhere by that time.