Adderall xr dosing

Patient: I was prescribed Adderall xr friendsor ADHD. I’m 36. Doc said to “play around” with dosing to find what is right for me. I have 10 mg XR pills. I have been trying last 3 days but no luck. If she wants me to take 2 10 mg xr pills/ day can’t I just take the 2 in a.m? Since they are extended release I’m not sure why I need to take 1 am and 1 afternoon. What do you think is best dosage? Can’t ask doc because she is out of town this week. Thanks!

Symptoms: N/a