Full Value and First Loss Basis

Managed to get a simpler explanation of "Full Value and First Loss Basis", compared to the contract document's version.
Made a mess in this definition today and sorry to my cousin.
(this term is mainly to explain the arrange for a property insurance).
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What is the difference between insuring on Full Value and on First Loss Basis?
When you insure on Full Value, the insurance company will pay you for the loss suffered but not exceeding the full value. If the sum insured is inadequate, Average will apply, i.e. you will have to bear a proportionate share of the loss.
When you insure on First Loss Basis, the insurance company will pay you for the loss suffered but not exceeding the first loss sum insured. If your loss, unfortunately, is more than the first loss sum insured, then you cannot claim the excess amount. Average does not apply.

How do I decide whether to insure on Full Value or on First Loss Basis?
The decision will depend on the nature of your goods. If there is a likelihood that all the goods can be stolen at any one time, then it is advisable to insure on Full Value.
However, if this is most unlikely, then you should insure on First Loss Basis, the amount of which depends on your estimate of how much is likely to be stolen at any one time.