Hi Ashoka,
You need to look at the 'Dampener (% of Total Capacity) Field' on The Capacity Constrained Resource Table.
Extract from the help:
"Specifies the tolerance as a percent that you will allow the critical load percent to be exceeded for this work or machine centre.
This tolerance percentage enables the program to schedule a load to a work or machine centre on the last possible day by slightly exceeding the critical load percent."
Regards,
Andrew