It usually is fairly obvious, but not a lightbulb moment. Sometimes especially hard to tell with non-amphetamines if they take a while to kick in like mine did, but amphetamines should be fairly easy to tell. I do know that everyone works differently, so if upping the dose again doesn't work you might want to try something different such as Adderall, or a non-amphetamine and see if it works better. It's not going to magically fully solve everything, you still gotta put work in (especially for executive dysfunction problems) but it should help a lot with focus, at least thats how it is for me.
Another thing is to maybe ask your doctor how best to take a short break to see how you feel on nothing vs the full dose closer together while paying more attention because slowly ramping up may make it hard to tell.
Btw, I'm on Quelbree (I think that's how to spell it) and it works ok for me, tbh I probably need to up the dose as well tho.