Side effects of GENERIC Adderall XR?

I just started taking a Generic version of Adderall XR for ADD. i was on Ritalin for a year in H.S. but stopped because if the feeling it gave me. Now my ADD is affecting my job performance so i talked to my doctor, so he put me on Adderall XR. but i bought the Generic version. It is Amphetamine ER 20mg. Capsule Imprint says M. Amphet Salts 20 mg. it is a Teva product. Doctor prescribed Adderall XR but i got the Generic version because of cost differences. today was the first day i took it. 1 pill in the morning as directed. the symptoms i felt were a little dizziness and just a little awkward feeling for the first couple hours and it took about 30-45 mins to work after taking. it seemed to be strong at first then not so much the rest of the day. is this normal since its new to my body? will it do it again each time i take it in the future? pharmacist said it could cause dizziness for about a week or little more. i was reading about adderall xr and it is suposed to have a smooth start and a smooth finish. this gave me a strong start and a smooth finish. and what does different MG dosages actually do. 10 vs. 20 etc.