Whenever you place an order with your courier company, you're going to have to give them an accurate description of your shipment. Along with things like size, weight, and anything special they need to know about the package such as if it's especially fragile, you're also going to have to provide your IL messenger service with a number that is known as declared value. Essentially, you're telling the courier how much your package is worth.
Declared value is a number that needs to be on a number of the forms that a courier will send along with any given shipment. This is the number that is used in case the package is ever damaged and an insurance claim is required. Typically speaking, the most that you would be allowed to claim as damages on your package would be the initial declared value or a percentage thereof as determined by the insurance company.
When filling out shipping forms, declared values have maximum amounts that you need to be aware of. Even if your package is worth much more than what the maximum declared value is, you still can't put more down that that maximum number in this area. That is because that is the maximum amount that an insurance company will pay out, regardless of the actual value of your shipment.
This is why people that regularly ship things which are extremely valuable often have questions for their couriers about the maximum declared value on any given shipment. If the maximum declared value is more than a small amount lower than the actual value of the shipment in question, usually the company that is shipping the product has to look into choices for ways to add more insurance to the shipment.
Sometimes the difference between actual value and declared value can be small. Usually a small difference means that added insurance coverage isn't worth enough to warrant the cost of the insurance itself. This is certainly not always the case though. Sometimes the insurance is going to be much less than what your products are actually worth. If something should happen to an order like that you could potentially face a massive loss. Companies avoid this by buying their own insurance to supplement that provided by the courier. Sometimes courier companies will have deals with their insurance companies to expand coverage directly through them rather than through a separate insurance carrier.