I don't know whether I can explain it on the level that you're looking for, but I'll share what I know.  The miners and masternodes each get their 45% of the block reward with the creation of each block, as you'd expect, but the 10% for the treasury is not created at that time.  Meanwhile, proposals for funding are submitted, as can be seen at http://dashcentral.org/ and are voted on by the masternodes.  Everything that requires funding, including proposals by the core team and developers salaries, must be submitted before the end of the cycle so that the masternodes can vote.  Then, approximately once every 28 days (there is a formula for the periodicity but it's quite complex), a superblock is mined with the sole purpose of paying out the funds to those proposals which passed the MN vote, from the 10% share of block rewards that was withheld for the treasury.  The winning proposals are funded directly and automatically from the superblock, so they receive freshly minted coins and there is no middle-man trusted to hand out the funds.  Any unallocated part of the treasury funds is just not created.