The + sign in front of a number for example, +350 means that a bet has been placed on the underdog, and the three digits following that sign indicate the amount paid out if the bet wins and the bettor had wagered $100.
If you were to bet $10 on +225 odds you would receive $22.50 in profit if this outcome won. Odds accompanied with a positive sign (+) indicate that this is the underdog and this outcome will have a lower chance of winning compared to a favorite, however underdogs will yield a higher profit if they win.