To redistribute assignments to annotators by percentage:

• Go to your project's tasks (see Tasks button on the left side of the screen). 
  
• Enter the task you want to redistribute by pressing it.
• In the "assignments of task" you can see the assignment inside the task (that needs redistributing).
• Click the 3 dots on the right of the assignment.
• Click the "Redistribute" button. 
• Uncheck "Auto Disperse" and manually assign different portions - make sure to reach 100%.

For more information please go to Assignments Page.