if a bookmaker quotes pay off odds of 99 to 1 against a particular horse... if a bookmaker quotes pay off odds of 99 to 1 against a particular horse winning a race, does that suggest that the chance that the horse will win is 1/100, less than 1/100 or more than 1/100?

I tried doing this on my own but saying "Oh it's subjective so it depends on whether or not we trust the bookmaker's intuition" and then I realized I was messing up the definitions between chance and odds. Can someone please help me this? 

Thank you so much in advance.
odds against = unfavorable occurrences : favorable occurrences,

whereas probability = favorable occurrences / total occurrences,

thus odds against of $\;99:1 = \dfrac1{99+1} = \dfrac1{100}$
99 to 1 odds just means money is staked more in favor of other horses.  This does not necessarily reflect the actual probability of a horse winning a race.

If you assumed the odds were a literal interpretation of the actual statistical outcome then 99 to 1 would mean 1/100 probability.  
1/100 = 1/100

You can find more info here about it in the link below.

Odds