The paramutuel (the "tote" in British terms) figures the odds from moment to mement by how much is bet on the horses altogether. If there are (say) five horses in the race, and $4 is bet on each of three of them, $2 on one, and $6 on another, for a total of $20 bet, then the one bet at $2 goes off (theoretically) at 10-to-1, the three with the $4 bets at 5-to-one and the one bet at $6 at 10-to-3. (Actually, the Tote takes a percentage of the handle, so the odds aren't going to be that exact, but it's close. The Tote may also gets the "breakage" - when a bet doesn't work out to an exact amount, like 10-to-2, which is properly 3.33333... to one, they would pay out $3.33. Doesn't sound like much - but imagine how much it might come to on a million dollar handle...)
So the odds are 25 to one because the heavy money is on other horses. The favourite may well go off at 4 to 5 or so, which means that your win on it would be less than your bet (though you get your bet back, too, so you make some money)
Race course gambling doesn't work like that.
The paramutuel (the "tote" in British terms) figures the odds from moment to mement by how much is bet on the horses altogether. If there are (say) five horses in the race, and $4 is bet on each of three of them, $2 on one, and $6 on another, for a total of $20 bet, then the one bet at $2 goes off (theoretically) at 10-to-1, the three with the $4 bets at 5-to-one and the one bet at $6 at 10-to-3. (Actually, the Tote takes a percentage of the handle, so the odds aren't going to be that exact, but it's close. The Tote may also gets the "breakage" - when a bet doesn't work out to an exact amount, like 10-to-2, which is properly 3.33333... to one, they would pay out $3.33. Doesn't sound like much - but imagine how much it might come to on a million dollar handle...)
So the odds are 25 to one because the heavy money is on other horses. The favourite may well go off at 4 to 5 or so, which means that your win on it would be less than your bet (though you get your bet back, too, so you make some money)