A bit is defined as a limitless notion of time, uniquely varying based on the situation.
I will be back in a bit may mean an hour, few minutes or a few days etc depending on what chore is being performed. Usually a common sense judgment maybe applied. When going to the loo a bit may range between 5 to 15 minutes an when going grocery shopping the same may mean a few hours, when travelling a few days, or during busy season more.
