(Answering to question by @hjt534, posted as “answer”; hoping that it would also answer the original question)
Your document is generated by Apache POI. It has zeroes in place of all calculated values, like this:
<row r="9">
<c r="A9" t="s" s="3">
<v>18</v>
</c>
<c r="B9" s="4"/>
<c r="C9" t="n" s="5">
<f>50.00</f>
<v>0.0</v> <!-- <========= this -->
</c>
<c r="D9" t="n" s="5">
<f>(C9)-(B9)</f>
<v>0.0</v> <!-- <========= and this -->
</c>
LibreOffice does not automatically recalculate cached values in opened XLSX by default - see this setting:
You may change the setting; and you may press Ctrl
+Shift
+F9
to force recalculation of everything in the file.