The Options dialog also allows you to control how Project calculates the costs of your project and how the critical path is calculated. This section explains how to set these options.
Setting the Cost Calculation Options
This option lets you define how the Actual Cost for tasks within your project is calculated. Those new to Project should leave this option checked.
This option controls how the Actual Costs that are entered by the user are distributed when Project breaks down the number across time.
This option lets you set the Default Fixed Costs Accrual for new tasks. It controls how Project spreads fixed costs out across the duration of the tasks.
Click the Earned Value button to set which % Complete measure and which baseline is used by Project to perform the Earned Value calculations.
This option defines whether Project will use % Complete, % Work Complete, or Physical % Complete when calculating Earned Value.
Project allows 11 different baselines for a project. Use this option to define which baseline should be used for Earned Value calculations.
Setting the Critical Path Options
When checked, this option tells Project to calculate a single multi-project critical path across all the projects that have been inserted into a master project.
Checking this box tells Project to show each independent chain of tasks as their own critical path. Activating this option might be a good idea if your projects contain several chains of tasks that are not linked together.
By default, a task is critical if its Slack field is equal to or less than zero. You may want to make the critical path calculation even tighter by saying that a task is critical if it has Slack of one day or less. Set this option to define when a task is considered to be on the critical path.
For Your Information
The Critical Path
The critical path of a project is the task or chain of linked tasks that determines the finish date of the project. By definition, any task on the critical path cannot change its finish date without changing the finish date of the whole project. The critical path is a very important focus point for the project manager because if a task on the critical path slips even one day, the whole project slips one day. Tasks not on the critical path have slack. Total Slack represents how many days the task's finish date can slip before it becomes critical.
This option lets you define how the Actual Cost for tasks within your project is calculated. Those new to Project should leave this option checked. 
This option controls how the Actual Costs that are entered by the user are distributed when Project breaks down the number across time. 
This option lets you set the Default Fixed Costs Accrual for new tasks. It controls how Project spreads fixed costs out across the duration of the tasks. 
Click the Earned Value button to set which % Complete measure and which baseline is used by Project to perform the Earned Value calculations. 
This option defines whether Project will use % Complete, % Work Complete, or Physical % Complete when calculating Earned Value. 
Project allows 11 different baselines for a project. Use this option to define which baseline should be used for Earned Value calculations. 
