The mint worker must of had a liquid lunch that day. It is a bit unusual to see a mm so close to the number, usually they are somewhere below. This would not be rare though as there would probably been at least 800 thousand Lincoln's struck from that die, more than likely more.
Well a lesson is learned. You now know that is normal, and you can move on to the next coin. But if you have a question, always ask. The dumbest question is the one not asked and the student assumes something instead. Ask. We are all family here and lessons learned, helps speed up the search for the real coin you want to find.