I’m guessing that lifting a bag of fertilizer, you probably use both your arms, right?

[So yeah, that would be pretty different, unless he’s assuming too much when he says it.]

Forty pounds on one arm is pretty ambitious. [Another assumption. She just looks a bit inexperienced, that’s all.] No shame in starting smaller, you know.

[She could tear something, and that would be no fun, but he doesn’t exactly want to jump into lecture mode with a random stranger.]