There have been a few different explanations of the conditional third-round pick in 2016 that Buffalo got from St. Louis in the Ryan Miller deal.
The full rundown:
If the Blues either re-sign Miller or reach the Western Conference finals, then Buffalo, instead of getting that third-round pick, gets the Blues' first-round pick this June (they have the first-rounder in 2015 from this deal); but St. Louis would then get Minnesota's second-round pick this June (obtained earlier by the Sabres) plus Buffalo's third-round pick this June.
The thinking here for St. Louis is that, although they would be giving up another first, it would be a pick between 27th and 30th overall and they'd be moving back just 15 to 20 slots or so by getting the Wild's second-rounder plus getting an early third-rounder (from Buffalo).
So, under this scenario, the Blues would have three second-round picks this June plus two third-round picks.
That's if they reach the conference finals or re-sign Miller.
If Blues don't advance to the conference finals but sign Miller to an extension after the 2014 draft, the conditional pick becomes a 2016 2nd-round pick.