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

• FTE-- the amount of time base 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, but that FTE equates to 8 hours per day regardless of a user's business week.   That is -- if you request 1 FTE for a week -- a user that has a business week with less than 40 hours would not be considered available for that effort.