Is Backlog Refinement a Time-Boxed event?
Can anyone help to understand 
 " Refinement usually consumes no more than 10% of the capacity of the Development Team." 
  
 Here is my understanding : 
  
 Estimated Capacity of a team = Committed dev team members x( Effective Hours x No.of Sprint Days)  
  
 Hypothetically  team members is = 4 (Fully committed) 
 Effective hours/per person  = 6 Hrs 
 No. Of Sprint Days  = 20 days(1 month sprint) 
  
 So the Capacity = 4*(6*20) =  480 man hours. 
 10% of 480 is = 48 hours which can be spent for the product backlog refinement. 
  
 Is it Time-Boxed? 
 do we need to convert this as a time-boxed of 2 days or 48 hrs  for a sprint of one month? 
 in this case the time box varies based on the effective hours invested based on person's focusing factor. 
  
 Tnx
No, backlog refinement is not a timeboxed event in Scrum. It's a responsibility of the Scrum Team, and one to be fulfilled within each Sprint timebox. The 10% figure is merely a guide to help shape an activity that should happen on an ongoing basis.