Adding another person to a planning row can mean sharing existing work or adding participation. Those are different assumptions. Write down what should remain unchanged before asking the scheduling model to recalculate.

Use automatically scheduled practice tasks in Project desktop for Windows. Microsoft relates Work, Duration and assignment Units. Task type controls which quantity is preserved when another changes. Double-click the task, choose Advanced and inspect Fixed Units, Fixed Work or Fixed Duration. For example, changing work on Fixed Units recalculates duration; changing work on Fixed Duration recalculates units.

Separate a shared workload from a meeting

Imagine an eight-hour checking job that one person can divide evenly with an equally available colleague. The arithmetic model is eight person-hours divided by two full-time equivalents: four working hours. That is a deliberately simplified assumption to test, not a productivity forecast for real people.

Now consider a one-hour briefing where both people must attend throughout. Its duration remains one hour, but attendance consumes two person-hours. Halving the meeting length or assigning each attendee only half the hour would fail that stated requirement.

Effort-driven scheduling preserves total work when resources are added or removed after the initial assignment. It does not apply to the first assignment in the same way. Fixed Work always uses it. For the briefing trial, inspect Fixed Duration and clear Effort driven in Advanced so additional participation is not merely redistributed existing work.

Inspect the result at assignment level

For the checking trial, choose Fixed Work. Build the two examples separately. First record the initial person, duration, work and units, then add the second person. In the checking example, look for the planned sharing of eight total hours. In the briefing, verify one hour for each attendee and two hours altogether.

If the result differs, identify exactly which quantity changed rather than repeatedly changing the task type. Keep the initial-assignment step distinct from adding someone to an already assigned task; otherwise two apparently similar trials can begin from different states.

Before applying the model to real work, confirm whether tasks are divisible, whether people can work concurrently and whether calendars permit the assumed overlap. Training, handover and waiting can invalidate a simple division. Accept the scheduling result only when its preserved quantity matches the work being represented.

Sources: Microsoft: task types; Microsoft: supporting procedure.