It's science

Lol but seriously, I have to point stuff like that out all the time in the gym. Somebody is adding 10lbs, and then they decide they might as well add 20 instead because that would put the working weight to 300 or whatever arbitrary barrier they're eyeing, and then they're amazed that it's too friggin' heavy when they just added 100% more than they were scheduled to add to the progression.
People forget that the devil is in the details, because with weights (and money) the details are often more relevant than they realize.