MR.TODD

I am looking to buy an M4 but I am a little confused on the capacity. On this website it says the capacity for the M4 is 4+1... However I see guys online talking about 7,8,and 9 round capacities using 2.75" shells? I don't know which specs are up to date... If I were to buy one today, how many 2.75" shells would it hold? Also, there are no legality issues to consider when increasing the mag capacity (for now) right? Thanks!