The deadline time is always the deadline – so if you weigh in just after the last deadline time, then you can have almost 24 hours to catch up. If your deadline is midnight, then if you weigh in at 00:01, you have 23h 59m to get back on track. If your deadline is midnight and you weigh in at 11am, then you’ll have 13 hours to get back on track.
You change your deadline under the goal’s settings section. If you generally weigh in at 11am, then I’d make the deadline 10:59am or something like that, for instance.
Does that clear that up a bit? Basically, you can’t say “I always want 24 hours from when I entered a datapoint to get a weight that’s under the line”, but you can set up the deadline so that if you weigh in at around the same time each day, you’ll have roughly 24 hours to weigh in lighter (as long as you do it before the next deadline).
“Ratcheting” is the process of removing safety buffer so your goal is due sooner. So if it’s at 101 days now and you want to be in the red today, you’d put in 0 and press ratchet.
It’s a bit more complicated for weight goals, because the amount of leeway you have can differ dramatically from day to day (e.g. I’ve gone from having 70 days of leeway to only having 50 in the course of one day where I weighed in heavier for some random reason – and then the next day went up to having 75 days of leeway)! Usually I’d err on the conservative side when ratcheting a weight goal, as a consequence, and only ratchet away a bit, see how it goes for a few days, and then ratchet a bit more.
The fluctuation buffer is designed to prevent you derailing due to random daily fluctuations in weight, e.g. due to drinking more, and you told us that the amount your weight can randomly vary is 1.5 units, so that’s the amount we add back on top of your current weight when putting you back on track. If you don’t want to have fluctuation buffer and you don’t want any leeway after a derailment, you can change your respite settings so you have 0 days of buffer and 0 fluctuation buffer.
To put it another way, the number of days of buffer is the number of days we set the rate to 0 for after a derailment, and fluctuation buffer is the number of units extra we give you in order that you won’t derail due to a random day where you drank more water, or whatever.