I've been monitoring retirements at United since the new limit was enacted. There have been an average of less than 2 per month since it started. The latest System Schedule Committee report shows 2 retirements in November. Prior to the age change, we were seeing ~25 retirements/month.
I'll be happy to dig through the reports and post the exact retirement numbers for United over the last two years if you do the same, including airline and monthly numbers. You never stated the airline for the 163 retirements. I'm assuming that you're only referring to Delta numbers since that's where you're employed. If you've added AMR numbers into that tally, I've got some 'news' for you about a special circustance that caused the numbers to spike.