The  Budget In  selection criteria is required and you must specify either:

• Hours -- the number of hours you would like to plan or assign for this user

• Utilization-- the amount of time based on a Full Time Equivalent value that you are looking to plan or assign.  
  
  Note that the user's business week definition will be used in conjunction with this calculation to determine their availability. For example, if you have a 20 hour business week, then 4 hours per day is considered to be 1 FTE, or 100% utilization. Two hours per day is .5 FTE, or 50% utilization.