I'm not sure I understood it correctly, but betting odds can change drastically? Can then change after I make a bet, or is my bet locked it at a time I made it?
This system uses parimutuel betting, so odds are not fixed until betting ends.
You can see the current odds when you're placing your bet, but those odds may go up or down a bit, depending on how people after you bet. Everyone gets the same odds once betting ends.