https://community.cloudera.com/t5/Support-Questions/Using-Apache-Nifi-How-can-you-perform-a-mathematical/m-p/285370#M211777 <P><a href="https://community.cloudera.com/t5/user/viewprofilepage/user-id/45715">@fowler7878</a>&nbsp;</P><P>&nbsp;</P><P>No problem.&nbsp; At this point you have extracted the the count successfully and used updateAttribute processor to subtract 31 from it.&nbsp; You do not need to write it back to the content to use it in putEmail processor.</P><P>&nbsp;</P><P>The majority of the putEmail processor configuration properties support NiFi Expression Language also.<BR />You can retrieve the value of your FlowFiiles attribute with this simple NiFi EL statement:</P><LI-CODE lang="markup">${COUNTFILES}</LI-CODE><P>So you can use above anywhere in the string you configure in the the "Subject" and/or "Message" configuration properties.<BR /><BR />Thanks,</P><P>Matt<BR /><BR />If you found my answer help you to a solution, please don't forget to mark it as the accepted solution.</P> Wed, 11 Dec 2019 19:06:30 GMT MattWho 2019-12-11T19:06:30Z