Your winning bid took you one step higher than the previous highest. You can look up how bidding works on eBay's help, but here it is anyway:

So, if the highest bid below yours was £20 then your bid of £20.63 would win, just as it would have done if the other bid had been £20.01, £20.50 or £20.62.
You should read the help to be confident in your bidding.