user40554: A while back, a friend told me dash had the same supply limit that bitcoin had of 21 mil.  I read on wiki recently that it's now 19 mil.

Estimated 19 million coins maximum, with a 7,1% decrease in the number of coins 

Did this change?  How can it be increased?

user10377: Might want to examine Section 5.2 of a Dash White Paper.  Here is the relevant code concerning Dash's monetary policy. 
It is difficult to project the exact amount of Dash currency that will come into existence because it appears to be a function of network difficulty, not block number or time.  However, hard limits in the code appear to set upper and lower bounds in the graph of the Dash White Paper. Plus funds not fully allocated by the Dash Treasury by masternodes (the Superblocks, associated with 10% of the block awards) are burned which reduces the overall supply.
Also ran across this Dash Detailed video that provides an explanation.  
It is worth noting the that the factor of ~7.14% (written as 1/14 in source code) approximately fits the Rule of 72 divided by 10, which means the amount of inflation is cut in half roughly every 10 years.

40554: <p>A while back, a friend told me dash had the same supply limit that bitcoin had of 21 mil.  <a href="https://en.wikipedia.org/wiki/Dash_(cryptocurrency)" rel="nofollow">I read on wiki recently that it's now 19 mil</a>.</p>

<blockquote>
  <p>Estimated 19 million coins maximum, with a 7,1% decrease in the number of coins </p>
</blockquote>

<p>Did this change?  How can it be increased?</p>
 10377: <p>Might want to examine <a href="https://www.dash.org/wp-content/uploads/2015/04/Dash-WhitepaperV1.pdf" rel="nofollow noreferrer">Section 5.2</a> of a Dash White Paper.  Here is the <a href="https://github.com/dashpay/dash/blob/master/src/main.cpp#L1537" rel="nofollow noreferrer">relevant code</a> concerning Dash's monetary policy. </p>

<p>It is difficult to project the exact amount of Dash currency that will come into existence because it appears to be a function of network difficulty, not block number or time.  However, hard limits in the code appear to set upper and lower bounds in the graph of the Dash White Paper. Plus funds not fully allocated by the Dash Treasury by masternodes (the <strong>Superblocks</strong>, associated with 10% of the block awards) are burned which reduces the overall supply.</p>

<p>Also ran across this <strong>Dash Detailed</strong> <a href="https://www.youtube.com/watch?v=2vZDclyqh5Y" rel="nofollow noreferrer">video</a> that provides an explanation.  </p>

<p>It is worth noting the that the factor of ~7.14% (written as 1/14 in <a href="https://github.com/dashpay/dash/blob/master/src/main.cpp#L1776" rel="nofollow noreferrer">source code</a>) approximately fits the <a href="https://en.wikipedia.org/wiki/Rule_of_72" rel="nofollow noreferrer">Rule of 72</a> divided by 10, which means the amount of inflation is cut in half roughly every 10 years.</p>
