i just recently purchased with a credit card 12 months of XBL. Since toy r us is running i get one access. and get the second 1/2 off. I bought i a 12+1 xbl card. so here is my question if i redeem it now will it add onto what i already bought? making it 25 months?? or will it overlap it??? thanks in advance..

I believe you can stack up to 3 years on your account. So you should be fine by adding it now.