Two things.

First, the first 1-2 days of ADHD meds can have a dramatic effect that have you thinking "this can't be right". It's normal, expected, and goes away very quickly. You should be warned to expect it by the prescribing doctor. After 3 days or so you barely know you're taking them.

Second, the dosage and effect on a non-ADHD person is entirely different to that an ADHD person will get. That's presuming it's the right med for them[0]. You will have a stimulating, speed, effect. An ADHD person (well most) will get little to no stimulation, and a calming effect, and might sit down to do their homework, or even just sit still for a couple of hours - for the first time ever. Amphetamines don't do that to normal neurology, thus you can't compare.

The dosage is putting them closer to typical, but putting you far away from typical. If you were normal vision or long sighted and tried your friend's short sight prescription glasses you wouldn't wish their glasses were weaker, would you? Same principle.

It's also common for one or other parent to discover they have it too after they have tried their child's meds.

[0] Getting the right medication is a bit of a trial and error minefield, but should be a standard part of treatment. Not all doctors are as willing to switch medication or titrate dosage as they should be.