Due to the nature of the equipment used in the manufacturing industry, it is not always possible to produce an exact quantity for a given custom order. While we make every effort to ensure each customer receives the exact quantity of product they ordered, on custom orders, occasionally there are slight overages/underages.
Overage is the additional quantity that is manufactured that exceeds your requested quantity. Conversely, underage is the quantity that is manufacturing that falls short of your requested quantity.
Why does this happen? In manufacturing, producing a particular quantity of pieces is not an exact science. Stopping the machine is a process that will sometimes produce more or sometimes less just by virtue of how the equipment works. One way to think about it is a car doing a hard brake. If the car is driving faster or on a wet road, it may take longer to stop than it would if it was driving slower or stopping on dry road. An immediate stop would be virtually impossible in wet conditions.
Less overage/underage can be expected for longer runs, while there can be more overage/underage expected for shorter runs.