As far I know 100 reputation would be deducted from my account if I do that?
26 is what is left after the bounty. A bounty is removed from your rep the moment you offer it, not when you award it to an answer. You lose that rep even if you don't then offer it to anyone.
Essentially the user gets 1 rep when joining, received an association bonus of 100 for having sufficient rep on another SE site, earned 25 points on AD to total 126, then gave 100 away for the bounty.