The arithmetic is simple
Using a consistent 0-to-10 effort scale, a hypothetical 30-minute session rated 4 produces 120 arbitrary units. A 60-minute session rated 2 also produces 120.
Those equal products do not make the sessions interchangeable. One is shorter and harder; the other is longer and easier. Exercise mode and local loading may differ as well.
Keep the rating convention stable
Decide whether duration includes warm-up and recovery, and use the same approach over time. Also keep the timing and wording of the overall effort question consistent. Otherwise, an apparent change may partly reflect a changed measurement method.
The score is most interpretable within a person's own history. A rating of 5 from two different people does not establish identical physiological demand.
Preserve the session underneath the summary
Record the activity and any unusual circumstances beside the number. “120 units, easy cycling” and “120 units, hill intervals” contain very different information.
A workload score can help notice changes worth discussing, but it cannot determine a safe weekly increase by itself. Turning a convenient summary into a rigid prediction of injury gives it more authority than the calculation supports.
