A kilogram plate set and a pound plate set produce different numbers for the same visual load. Two red plates a side reads as 225 lb on an American bar and 100 kg, roughly 220 lb, on a competition kilo bar. The gap widens as the bar gets heavier, so four plates a side means 405 lb in one gym and 180 kg, about 397 lb, in another.
Powerlifting federations compete in kilos, which is why meet attempts often look like odd numbers to pound-trained lifters. When you move between gyms or follow a program written in the other system, convert the total first and load from the plate set in front of you. Loading 100 kg worth of pound plates lands you at 220.5 lb, and chasing round numbers in the wrong unit adds weight you never planned to lift.