I don't think it's possible to get placed into Bronze 5 for your first time placements.
The baseline MMR is somewhere in Silver, so first time Rankers begin with an ok MMR that their placements will affect. For people that have placed in Ranked in a previous season they will already have MMR, but some of them trash theirs so the next season they place lower than a brand new player can.
Since you've placed for this season now, next season your placement will begin at whatever you get it to (so try to raise it up so you don't get placed in Bronze). Everyone loses some MMR in a "soft reset" with a new season if they ranked previously, so if you stay with Silver V MMR you'll probably place in mid-high Bronze next time. You'll be able to raise your MMR during the preseason if you want (the time between this season's end and the beginning of next).