The screenshot you uploaded shows you are trying to allocate a total of 34.5 leave days for the month of August 2018 which has 31 calendar days.
If any of your employees were to proceed on leave in August 2018, that employee cannot have more than 31 days, because August 2018 does not have more than 31 days. That is what ERPNext is simply saying.
Since your leave period is one month, it is not going to be possible for an employee to have leave days allocated to him or her over and above the number of days in that same month.
You may have to consider using Year as your leave period, if your employees are supposed to have more than 31 calendar leave days allocated to them.
1 .Unused leave is 33 and month of aug allocation is 1.5 (monthly earn ) bez auto earned system not work and i allocate manually and message shows
2. bez in our organization 2 year leave earning system