How can I customize estimation different for each month and not total workload equally diivided for

[Saumya Gupta]

How can I customize estimation different for each month and not total workload equally divided for duration. If I log work or issue and effort estimation it automatically divides the time into equal hours for the months 

Example 100 hrs May to Aug 21 ie 4 months. 

                        May           Jun         Jul      Aug

Jira Default      25h             25h         25h     25h          100/4=25 hrs per month 

Required         10h              40h         40h     10h          tot 100 hours per requirement 

How can I add estimation in required form on Jira?

Thank you