All length estimates and mileages are for round-trip. If a hike is an out-and-back type hike, the distance is both out and back, not one way. If it is a point-to-point type hike, the distance is the full length point-to-point.
Mileages given are taken from GPS tracks and should generally be pretty accurate. Your mileage may be off a bit due to side trips and/or GPS variablility.
Length is a quite variable depending on the group. Time ranges are based on my experience. Usually, my groups are small and average fitness levels, BUT, we generally don't often stop for breaks. When we do take breaks along the way, they are usually relatively short. Our hiking speed is generally about two miles an hour, maybe 2.5 if it is well used and easy trail.
So, the time at the bottom end of the time range is the time our group took, the upper end is the time I think an average fitness level group with a few more breaks will take.
If you take a lot of photos, have navigation issues, take long breaks, or are a bit slower of a hiker, your time may be quite a bit more than the time estimate given.
Important: Particularly in technical canyons, groups size and experience level of ALL members of the group matter! A 4-hour romp for a competent small group can turn into an all-day epic for a group of 12 with a few newbies thrown in! Start with smaller/easier adventures with a small skilled group before tackling larger objectives or bringing along newer folks.
Virtually all of the groups that I have corresponded with that have had epic overnight adventures have been intermediate level leaders taking a large group of inexperienced friends in an intermediate canyon. Keep beginners in beginner-friendly terrain!