SCRUM is a specialized version of agile project management methodologies. In Scrum each iteration is called a scrum, Here iteration period can be a 1-2 Months. A client priorities his requirements what he want first. If developer did not meets all the requirement which was being fixed for a particular scrum than rest of the development part would be transferred to the next scrum (would be delivered in the next build), means developer can’t increase time decided for a scrum. It’s fixed.
The idea behind Scrum is to create a streamlined project management process that produces a quality end product.
Because the scrum process also provides much room for individual work and contribution, developers are free to devise ideas and solutions. Usually these ideas are pioneering and innovative as the team relies on the best possible formula for the completion of their work, in order to finish the project as appropriately, and as efficiently as possible.