That is correct, the winning odds change after you place a bet because you're against other users and not the house.

The total bet on Barcelona is about BTC0.186 let's say their all of their weighted multiplier is at 100% while the BTC1 bet by coinlockets is at 95% only using the 95% since it's the current weighted while im making this post.

Using the formula provided from the site you'll end up with this.

The rest share (100/(95+100)) or 51.3% and for coinlocket he'll get 48.7% or (95/(100+95)).

If he drops a BTC1 bet it would cause the odds to drop by a lot and he would win approximately BTC0.136.

 From how I understand it does affect the odds because the profit you'll get depends on the weighted multiplier and not just the bet amount alone.