Lobna,
The employee that you are receiving the error for needs to have absence quota for the particular absence quota type that the absence itself deducts from. If you check infotype 2006 then you will see that the employee either has no quota entitlement remaining or has less quota entitlement remaining than the amount of time you are entering for the absence.
If you want to give the employee quota you can give them an infotype 2013 record to transfer some entitlement hours or if you have set up rules to generate the entitlement then just run time evaluation.
If what I've stated above doesn't seem like it will work for you then please provide some more details as to your requirement, and what your expectations are concening the absence you are entering and the quota deduction.
Thanks,
Kory