Thats is 'odds on' JD, meaning that you put more on to win less, for instance 1/2 (or 1 to 2 on) means you bet 2 to win 1 (total return 3 which includes your 2).
So if Taylor is 4/5 (5 to 4 on) you will place 5 and if he wins you will win 4, your total return is 9 (your 5 plus the bookies 4 (your winnings).
If MvG is 2/1 (2 to 1) then you place 1 and if he wins you win 2 (total return of 3) so if you matched the bet and also had 5 on MvG you would win 5x2, 10. This time your total return would be 15, consisting of your 5 stake plus the bookies 10, your winnings.
Hope that helps mate, any query's send me a PM and i will see if I can clear it up if you were thinking of a particular bet.