ADDERALL XR 2 X A DAY? HUH?

I DO NOT UNDERSTAND THIS ONE AT ALL!  I SEEN MY DR. TODAY AND TOLD HER THAT I WAS NOT FEELING TOO MUCH ON ADDERALL XR 10 MGS AND I STARTED ON MY OWN 20 MGS TWO DAYS AGO.

I'VE  HAD A TON OF BODY TENSION STUFF WHERE MY BODY FEELS LIKE IT IS ONE BIG KNOTTED MASS.  I KNOW I WOULD OF NEEDED TO GET USE TO IT AGAIN BUT INSTEAD SHE PUT ME ON ADDERALL XR 10 MGS TWO TIMES A DAY!

I DO NOT UNDERSTAND HOW THAT WHEN I TAKE ONE 10 MGS AND IT DOES NOTHING FOR ME, HOW ON EARTH WILL TAKING 1 TEN MGS IN THE A.M.AND ANOTHER 10 MGS 6 HOURS LATER DAY WILL DO ANYTHING.

CAN ANYONE EXPLAIN THIS LOGIC CAUSE I JUST DO NOT GET IT!