subtract two column in pivot table
<p>My source data looks like this screenshot 
<a href="https://i.stack.imgur.com/8Ahn3.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/8Ahn3.png" alt="Source Data"></a></p>

<p>I would like to know</p>

<ol>
<li>How many purchase order numbers (column <code>po no</code>) has each project?</li>
<li>How many <code>po no</code> I have received <code>in admin</code> until now?</li>
<li>How many remain?</li>
</ol>

<p>Using a pivot table i solved my first and second question.
To calculate the value for the <code>sum of remain</code> column i tried to use a calculated field but I got wrong results (see below).</p>

<p><a href="https://i.stack.imgur.com/kGikX.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/kGikX.jpg" alt="Using caclulated field to get the sum of remain"></a></p>

<h2>Desired result and question</h2>

<p>I would like to achieve to get a pivot table like the example table below.</p>

<p>How can create a pivot table where the colum <code>remain</code> is the result of <code>count of po no</code>-<code>count of po_in_admin</code>?</p>

<p><a href="https://i.stack.imgur.com/mNVhq.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/mNVhq.png" alt="Desired result"></a></p>