Difference between Quantity contract and Value contracts

Hello SAP experts!

What is the difference between Quantity contract and Value contract? Is my understanding (please see below) correct?

QUANTITY CONTRACT

>>A quantity contract is an agreement that your customer will order a certain quantity of product from you during a specified period. The contract contains basic quantity and price information but no schedule of specific delivery dates and quantities

>>Specific to certain quantity of materials and price (100 boxes of Material A for 100 usd/box)

>>Call-off orders with reference to the contract WILL NOT BE AFFECTED by any price movements made outside the contract.

VALUE CONTRACT

>>A value contract is a legal agreement with a customer that contains the materials and services that the customer receives within a specified time period, and for a value up to a specified target value. A value contract can contain certain materials or a group of materials (product hierarchy, assortment module).

>>Can contain group of materials/certain materials but not necessarily have a fixed price (Group Material XYZ up to a total value of 100,000 usd)

>>Call-off orders with reference to the contract WILL BE AFFECTED by any price movements made outside the contract, it will just eat up the contract value.

Appreciate your help.

Thank you.

Geric