That is the ICO tokens, there was roughly 134 Million that was sold in a Pre-ICO funding stage and the other 100 MIllion is going to bounties and such.
276 MM + 134 MM + 100 MM = 500 MM tokens
Scroll down on that dashboard page and click the first question in the General Questions tab
There will be 500,000,000 BOScoin tokens in circulation at launch. The token profile will be:
Fundraising events:
Preliminary Fundraiser : 133,906,311
Fundraiser Event : 276,093,689
Distributed (Stake):
Foundation : 40,000,000
Members : 40,000,000
Bounty : 10,000,000
Additional information regarding the distributed stake:
Foundation : The Foundation will use the set number of tokens to sustain a stake in the ecosystem and carry out the purpose of the foundation.
Members : Members who participated in the development of the BOS Platform receive a share of BOScoin tokens.
Bounty : Users who participated in the bounty program are rewarded BOScoin tokens.