This is a really unintuitive quirk of the way bounties are handled with relation to the association bonus.
Essentially, bounty reputation is always considered to be deducted from your "site" reputation. As long as you have enough total rep you can offer a bounty, but it never dips into your "bonus" reputation from associating your accounts, even if that puts you in the negative.
For the purposes of your reputation "on this site", Stack Exchange has calculated the following:
- Registered an account: 1 rep earned (total earned: 1, total rep: 1)
- Association bonus: 0 rep earned (total earned: 1, total rep: 101)
- Question upvotes: 40 rep earned (total earned: 41, total rep: 141)
- Suggested edits: 2 rep earned (total earned: 43, total rep: 143)
- Bounty offered: -100 rep earned (total earned: -57, total rep: 43)
This Meta SE question contains an official explanation from one of the staff. This behavior is extremely confusing.
I have unprotected the question for you. The reason I originally applied it was because it picked up some very blatant spam off of some very unintelligent keyword search bot. If it picks up more then it may need to be protected again, but in the meantime I'll just keep an eye out for any flags on it.