He didn't really see anything wrong with his potato but he leans closer to watch the technique that Senku is using s he drops it into the bin. He is a good study so he is sure that whatever error he has made that he can correct it.

He picks up the next potato and starts to mimic what he has been watching. "You can always work on your strength. The train has many options for that. Strength is just a first step towards being able to fight but there are people who can also teach you that."