A very common theme in project management/software engineering resources is that goals should be SMART. This question is targeted to the "M" in SMART: Measurable.
The examples commonly found in literature or lectures often times seem unrealistic and far fetched to me. See for instance this example:
Analyst Question: How much would you like to reduce your chemical expenses?
Executive Response: By 25% within one year.
Wiegers, Karl; Beatty, Joy (2013-08-15). Software Requirements (3rd Edition) (Developer Best Practices) (Kindle Locations 2180-2181). Pearson Education. Kindle Edition.
So a business objective is to reduce chemical expenses by 25% within one year. That's a great measurable goal. But it sounds extremely unrealistic to hear such a thing from a customer. The customer does not want to reduce expenses by 25% in one year, he wants to eliminate the costs altogether and he wants to do so immediately.
This would sound somewhat more realistic to me:
Executive Response: Within 10 years the software must have saved us as much money as we invested to develop it. Because if it does not we would better have invested our money in another project.
How do real projects get to those numbers?