I calculated it as "8 hours" figuring there were also stops for water, lunch, etc. In other words, it was a full day in adventurer speak, just not 24 actual hours of walking/riding through the hex. Same with when it requires 3 days to explore, etc. Its not 72 hours, but three adventuring days if that makes sense. Mainly, use it as a guide for when to roll random encounters and the like.
It's an 8 hour day. (Otherwise it would say "24 hours" or some such thing.)
Furansisuco, what's the context here? Do you have a player saying that they want to cut out some eating and resting to explore faster?
I mean, if a player has somehow gotten their character turned into an iron golem, it might be reasonable for them to ask to use the full 24-hour day for adventuring/exploration/travel, but so long as they're still mortal, they need to eat and sleep, and it takes time to make a campsite for the night and then break it down in the morning, and I would be all too happy to apply morale/exhaustion penalties to someone who was just sleeping on the ground, eating nothing but hard tack, etc. (Not to mention that they would likely contract scurvy/rickets/etc eventually, and would take huge circumstantial penalties to diplomacy checks for looking like the murder hobos they clearly are at that point.)
If characters want to travel/explore beyond the normal 8-hour activity cycle, there are rules for Forced Marches.
Forced March rules only cover movement, not activities like exploration, which are much more mentally strenuous. If you spend 20+ hours straight exploring, you're going to be way less observant towards the end and could miss landscape features that might otherwise be automatically noticed.