Macquarie Group provided a wide range of estimates of the level of its surplus capital at its full-year profit briefing. These estimates range from A$2.1 billion to $4.5 billion, though each measure serves a different purpose.Of this surplus, Macquarie now plans to buy back around $800 million. Of this, $500 million will be in the form of a conventional share buyback, with the remainder being purchases of shares to satisfy share issues to staff and the dividend reinvestment plan.This, in turn, represents less than one third of the $3 billion - at least - in surplus capital that Macquarie argued it held six months ago.The divergent estimates of capital reflect the analysis used to frame each estimate. The higher estimates are based on the Basel II capital regime that is being superseded, and the lower estimates are based on the Basel III capital regime that will replace it.In the latter case, the estimate is also based on capital requirements that will apply in 2016 but applied to the Macquarie business as it is today.Stephen Allen, head of risk management, told the investor briefing: "I would also holler that $2.1 billion, remember we are talking about the requirement that we must have on 1st January 2016. "But, of course, we've got earnings in the meantime and other initiatives that are going on."