Time works differently
Time works a little bit differently than some of the other aspects of FATE v.3.
When judging time, bear in mind that the steps are fairly subjective, depending on the setting. What might be a Mediocre amount of time to take one type of action could be an Epic amount of time for another type of action.
Sometimes it's backwards
Also remember that usually the time ladder is going to seem inverted. An Epic amount of time for an action would be a much shorter time period than a Mediocre time period. Exceptions to this would be in cases where a PC is attempting to maintain an action over an extended period of time.
Bob the Builder is attempting to build a new house for a customer. The GM judges that an Average amount of time this would take might be "a few months" (rung 16). Bob's Construction skill is at Great (+4), and he rolls a +2, giving him an Epic (+6) construction, which bumps his construction time down by 6 steps to "an afternoon" (rung 10). I guess he's just really good with a hammer.
Mace the Barbarian is attempting to hold open the gates of the Tomb of Quan Mulech, while his companions scramble through. The GM determines that - as the gates are made of solid stone - an Average time to be able to hold the gates open would be "a few seconds" (rung 2). Mace's Strength skill is at Good (+3), and he rolls a -1, giving him a Fair attempt to hold the gates open. This puts him at rung 4 ("a minute") to be able to hold the gates open. Either his friends will have to hurry or Mace will have to spend a FATE point to tag an aspect and increase his roll.