You can add trash until the compartment is full and the compactor will not compact the trash any further. The compact cycle time will be shortened as the compartment fills up. During full cycle the ram travels 2/3 of the way down into the trash bucket.
With Humalog's short action time of 3  hours, covering postmeal highs with more insulin can be considered as soon as two hours if a meal dose have been underestimated. Of course, not as much sliding scale insulin would be needed here as before a meal, because some of the meal dose is yet to work.
Since the first rapid-acting insulin, insulin lispro (brand name Humalog), came on the market in 1996, most diabetes experts have recommended taking it within 15 minutes of starting a meal (any time between 15 minutes before starting to eat to 15 minutes after starting to eat).