16 - 64 = Tier 1
64 - 256 = Tier 2
256 - 1024 = Tier 3
and so on.
If a Recipe is in a Tier that is below the Machines Minimum, its power gets multiplied by 4, and the time gets divided by 2, and that will happen until the proper Tier is reached.
If a Recipe happens to be right at the border between two Tiers (64, 256, 1024 etc) it will take the most benevolent option.