According to the SAFe® Agile Product Management APM (6.0) documents and learning resources,

Weighted Shortest Job First (WSJF) is a prioritization model used to sequence work for maximum

economic benefit. It is calculated by dividing the cost of delay by the job duration or size. To estimate

the cost of delay, three factors are considered: user and business value, time criticality, and risk

reduction or opportunity enablement. To estimate the job duration or size, a relative scale such as

Fibonacci is used. The highest value in the Fibonacci scale is set as the “ceiling” and the lowest value

is set as the “floor”. The items are then scored by comparing them to the ceiling and the floor, and

assigning them the closest Fibonacci number. The WSJF score is then obtained by dividing the cost of

delay score by the job duration or size score. The items with the highest WSJF score are prioritized

first.

Reference:

WSJF - Scaled Agile Framework

Weighted Shortest Job First (WSJF) | Definition and Overview - ProductPlan

Weighted Shortest Job First - Open Practice Library