The montly project budget page is a much more highly detailed look at your project budget expenses. You will notice on this page of the Excel project budget template that labor costs have been broken down into the individual employees, and that employee rates are given.
If you enter in each employee's day rate, and then how many days you expect to utilize the employee for a given month, you will see that the total cost for that employee is automatically generated.This makes it easier to budget for labor costs. For example, if you know you have a set amount of $50,000 to use on labor from your income/funding sources, then you will be able to determine exactly how often you can utilize each resource for your project.
You will, like with the budget overview page, want to account for risk in some way in your budget here. You can easily do this by inserting a line into the template page, and budgeting a certain amount of funds for each month's risk reserve. Alternatively, you can add a percentage of overage for each category each month to account for risk.