Visa Bulletin: Final action date vs dates for filing

Can someone the two charts on the visa bulletin page?
1) FINAL ACTION DATES
2) DATES FOR FILING.

My mother placed a petition for me in Sept 2013 under F1 category. So what exactly do these dates mean for me? The October visa bulletin for dates for filing shows: 01JAN12.

Are you adjusting here or do you need a waiver?

From what i understand for consular processing (visa granted abroad)

Chart a -final action is when they will issue an interview letter. If your date is before the cut-off, a greencard can be issued after passing interview, etc.

Chart b- dates for filing is when they will send a welcome letter and you can pay fees to National Visa Center, etc.

Now if you are adjusting status in the US
Chart a- an interview will be scheduled and you get your greencard.
Chart b- you can submit i-485 adjustment of status and you can receive ead while waiting for chart a dates to be current.

They can only issue visa/greencard if your priority date is current in chart a.

I'm just not sure when to file 601a waiver, wait for chart a or b.

Correct me if i'm wrong, this is what i understand on the visa bulletin chart

I would need a 601a waiver to do the consulate interview. I am trying to understand the exact timelines and process. I paid a lawyer for consultation back in 2013 but he didn't explain anything. Complete utter waste of money.

Bump...