I noticed his National Defense Service Ribbon is on the fourth row at the right. I was thinking there was an assigned order to the ribbons and the National Defense Ribbon went on the first row in the center. (It’s been nearly 50 years since I was in the service.)
Ribbons are worn according to order of precedence, so the placement of any single ribbon will be determined by it's "rank" relative to any other ribbon(s) worn. As such no particular ribbon will ever be worn in the same place, but will be ordered based on the number of other ribbons, and what they all are.