FTA: “In testing I knew that it was around 25 watts quicker”

What does that mean? My best guess is that, at speeds around his target speed, it takes 25 watts less power to ride at that speed, but that seems too huge a difference to give up on to me (https://cyclingtips.com/2021/07/1026-km-austrian-ultra-cycli... says the guy doing >1,000 km in 24 hours had a normalized power of 275W, so, assuming the two riders to be of similar weight, that would mean giving up about 10% of power))