So when I want to change my build number to some other number which is a higher value than current Jenkins is accepting in the set next build number, but if I want to set that to a lower value than the current, then Jenkins is not allowing that number. To configure it to lower values I have to delete all the builds and then reset to the lower build number I wish. Which, almost like creating a new job and starting a fresh build. It seems Jenkins only accepts build numbers in ascending order not in descending order. The issue that organizations have to face when they want to change the build number like (1000 is build number and wish to change it to 500(not used for that job) )this they have to lose the build data of previous ones which are not a good thing for any organization.