National processing time or service center processing time

[Elixir]

I had a question about I-485 approval. One the immigration.com website when I want to check the approval times there are two times that are are mentioned. One if the National processing time and the other is the local service center (CSC, VSC, MSC, etc.) processing times. Can someone please tell me which processing time I should be looking at?
Santosh

 

[ginnu]

you should check service centre like CSC, VSC or what ever is your service centre

 

[tonyhou]

what's the difference

but what's the difference for these two times ?
thanks